Writing prompt: How to Achieve Calmness

Student essay:
I once heard a story: an elephant was completely absorbed in eating while a fly constantly disturbed the elephant because it can't stay for a while in one place. The fly was so curious about how the elephant can stay calm and still that it asked the elephant about the secret to the calmness and the elephant tell the fly that the secret is just controlling the attention.
But how to control our attention? It's quite difficult to answer because calmness is an abstract word. We can't point to something and say 'Hey, this is calmness! '
I suppose that, 'a goal' is necessary to achieve calmness. If you have a goal in your mind, you will concentrate on reaching the goal, and the goal will have a subtle influence on you. Gradually you manage to get calmness.
Calmness is much important for us. On Thursday, we had a maths quiz. And during the quiz, my deskmate continuously disturbed me, I felt so annoyed that I can't focus. As a result, I failed the quiz.
So in the following days, I determined to concentrate on the study without any other thoughts. And achieve high grades in the next examination.

Corrected essay:
I once heard a story: an elephant was completely absorbed in eating while a fly constantly disturbed the elephant because it couldn't stay for a while in one place. The fly was so curious about how the elephant could stay calm and still that it asked the elephant about the secret to calmness and the elephant told the fly that the secret was just controlling the attention.
But how to control our attention? It's quite difficult to answer because calmness is an abstract word. We can't point to something and say 'Hey, this is calmness!'
I suppose that 'a goal' is necessary to achieve calmness. If you have a goal in your mind, you will concentrate on reaching the goal, and the goal will have a subtle influence on you. Gradually you manage to get calmness. Calmness is very important for us. On Thursday, we had a maths quiz. And during the quiz, my deskmate continuously disturbed me. I felt so annoyed that I couldn't focus. As a result, I failed the quiz.
So in the following days, I determined to concentrate on studying without any other thoughts and achieve high grades in the next examination.

Error analysis:
error_sentence: I once heard a story: an elephant was completely absorbed in eating while a fly constantly disturbed the elephant because it can't stay for a while in one place.
correct_sentence: I once heard a story: an elephant was completely absorbed in eating while a fly constantly disturbed the elephant because it couldn't stay for a while in one place.
error: ca
correction: could
error_type: Verb Tense Error
error_severity: 3
error_description: Verb Tense Error: Based on the context, the past tense should be used here to be consistent with the past event described in the sentence, therefore 〈can't〉 is changed to 『couldn't』.

error_sentence: The fly was so curious about how the elephant can stay calm and still that it asked the elephant about the secret to the calmness and the elephant tell the fly that the secret is just controlling the attention.

correct_sentence: The fly was so curious about how the elephant could stay calm and still that it asked the elephant about the secret to calmness and the elephant told the fly that the secret was just controlling the attention.

error: can
correction: could
error_type: Verb Tense Error
error_severity: 3
error_description: Verb Tense Error: Based on the context, the past tense should be used here to be consistent with the past event described in the sentence, therefore 〈can〉 is changed to 『could』.

error_sentence: The fly was so curious about how the elephant can stay calm and still that it asked the elephant about the secret to the calmness and the elephant tell the fly that the secret is just controlling the attention.

correct_sentence: The fly was so curious about how the elephant could stay calm and still that it asked the elephant about the secret to calmness and the elephant told the fly that the secret was just controlling the attention.

error: the
error_type: Determiner Error
error_severity: 2
error_description: Determiner Error: According to English grammar rules, the determiner 〈the〉 is unnecessary when describing the abstract concept 〈calmness〉, therefore 〈the〉 is deleted to conform to semantic rules.

error_sentence: The fly was so curious about how the elephant can stay calm and still that it asked the elephant about the secret to the calmness and the elephant tell the fly that the secret is just controlling the attention.

correct_sentence: The fly was so curious about how the elephant could stay calm and still that it asked the elephant about the secret to calmness and the elephant told the fly that the secret was just controlling the attention.

error: tell
correction: told
error_type: Verb Tense Error
error_severity: 3
error_description: Verb Tense Error: Based on the context, this describes a past event, the verb 〈tell〉 needs to be changed to the past tense 『told』 to maintain tense consistency.

error_sentence: The fly was so curious about how the elephant can stay calm and still that it asked the elephant about the secret to the calmness and the elephant tell the fly that the secret is just controlling the attention.

correct_sentence: The fly was so curious about how the elephant could stay calm and still that it asked the elephant about the secret to calmness and the elephant told the fly that the secret was just controlling the attention.

error: is
correction: was
error_type: Verb Tense Error
error_severity: 3
error_description: Verb Tense Error: Based on the context, this describes a past event, the verb 〈is〉 is changed to 『was』 to maintain tense consistency.

error_sentence: I suppose that, 'a goal' is necessary to achieve calmness.
correct_sentence: I suppose that 'a goal' is necessary to achieve calmness.
error: ,
error_type: Punctuation Error
error_severity: 1
error_description: Punctuation Error: According to English writing conventions, in an object clause introduced by 〈that〉, no comma is needed after the conjunction, therefore the redundant comma 『,』 is deleted to make the sentence structure more concise.

error_sentence: Gradually you manage to get calmness.

correct_sentence: Gradually you manage to get calmness. Calmness is very important for us.
error: 

error_type: Format Error

error_sentence: Calmness is much important for us.
correct_sentence: Calmness is very important for us.
error: much
correction: very
error_type: Adverb Error
error_severity: 2
error_description: Adverb Error: The usage of adjective 〈much〉 does not conform to idiomatic expression, 『very』 should be used to modify 〈important〉 to express degree. Therefore, 〈much〉 is changed to 『very』.

error_sentence: And during the quiz, my deskmate continuously disturbed me, I felt so annoyed that I can't focus.
correct_sentence: And during the quiz, my deskmate continuously disturbed me.
error: ,
correction: .
error_type: Punctuation Error
error_severity: 1
error_description: Punctuation Error: A period is needed to separate the two independent clauses 〈my deskmate...〉 and 〈I felt...〉, therefore the comma 〈,〉 is changed to a period 『.』 to avoid a run-on sentence.

error_sentence: And during the quiz, my deskmate continuously disturbed me, I felt so annoyed that I can't focus.
correct_sentence: I felt so annoyed that I couldn't focus.
error: ca
correction: could
error_type: Verb Tense Error
error_severity: 3
error_description: Verb Tense Error: Based on the context, the past tense should be used here to be consistent with the past event described in the sentence, therefore 〈can't〉 is changed to 『couldn't』.

error_sentence: So in the following days, I determined to concentrate on the study without any other thoughts.
correct_sentence: So in the following days, I determined to concentrate on studying without any other thoughts and achieve high grades in the next examination.
error: the study
correction: studying

error_sentence: So in the following days, I determined to concentrate on the study without any other thoughts. And achieve high grades in the next examination.
correct_sentence: So in the following days, I determined to concentrate on studying without any other thoughts and achieve high grades in the next examination.
error: . And
correction: and
error_type: Punctuation Error
error_severity: 1
error_description: Punctuation Error: The two verb phrases 〈concentrate...〉 and 〈achieve...〉 need to be directly connected by the conjunction 『and』, therefore the period 『.』 is deleted and it is changed to lowercase 『and』 to form a correct parallel structure.