I am one of the try-hards OP has described. I came to Canada at the age of 12 knowing very little English. In my first two years in Canada, my self-esteem and confidence dropped to a very low point because I couldn't keep up with my peers due to my poor English skills. Basically, I was not even allowed to take regular classes because my English was not good enough. I am not naturally good at learning language so I had to study very hard. My parents were not good at English and we didn't really have money for tutoring. I don't even think my parents really believe that tutoring would work; they always believe in self-learning. I eventually got better and got the chance to take regular classes. But my English still caused a lot of difficulty in understanding the course materials. Other students could easily understand the lecture and the textbook. However, to me, I could not understand anything the teacher said in class; so I had to read the textbook myself. The textbook was pretty hard for me; so I had to read two or three times. To my surprise, due to hard work, I was able to get the top marks in most of my classes. And the learning strategies I have developed along the way have helped me succeed in university as well.

I think OP definitely has "idealized" the people who could achieve top grades. I procrastinate a lot of times, wasting my time watching dramas and constantly interrupting myself with online chatting. I am not sure if I perform poorly under stress or not. But I am very very very prone to stress and anxiety. I think because that I recognize my limit (my predisposition to stress and anxiety), I always start things early so I don't have to stress out in the end.

It is not that good to get high marks all the time. Some people think I am simply a nerd who doesn't know how to socialize. They would also say that I only know how to get good marks but not know other things. Some people would think that I am an introvert who stays at home studying all the time... In fact, I love being around people, love hanging out with friends.. I love teaching, tutoring and giving out presentations.. There are a lot of stereotypical beliefs about nerds.. And these things made me very sad at times. But I feel that I had to work hard because I wanted to go to grad school and GPA is a big consideration when it comes to applying for grad school..

Anyways...all these rambling probably won't help OP gets good marks..I will provide some of the study strategies that have helped me succeed in school:
1) Prepare before you go to the lecture. Read the textbook before you go to the lecture. There are times when I preview the whole course material during the summer before taking the course... I think that is simply too extreme for other people..But I did that and it worked for me. When everyone was struggling to understand the materials, I already know most of it...

2) I record my lectures and listen to them like "music"? If the prof is good at lecturing, it is actually not that boring to listen to the lectures again. At times, the prof would give some possible hints about questions on the exams; those hints can be helpful at times.

3) Start on your hw early so that you can leave some time to ask questions. If hw counts a significant portion of the mark, you should definitely start early and ask the TA questions if you don't get any of the questions. Keep asking them until you figure out the answers. KEEP ASKING! It is funny that I eventually become a very friend with one of my TAs because I always go hang out with her during her office hour.

5) I know every well about my limit. So most of the times, I don't take too many courses to overwhelm myself. I also tried to balance my semester with some easy courses and some hard ones. Whether the course is easy or not depends on what you are good at. An English course can be easy for an Arts student to get an A but extremely hard to a science student.

6) Know about the teacher's testing strategies. Some profs like to ask questions from the textbook; some like to focus on the lectures more.. Some have really tricky MC questions.Some teachers like to test the conceptual stuff more. Every prof is different. Knowing what the teacher's testing style is very important.

7) I don't know how relevant it is to other people but TAs have marked my exam wrong multiple times.... It happened to my friend also. There was once when the TA gave me 76 when I got 95.. There was also another time when I got 95 on an exam after crazy scaling. I thought this time, they probably marked everything right and I didn't need to check my exam with the TA; but I eventually went to check it before my final just in case there were some similar questions on the final. And they marked a written question wrong again. Maybe I am just bad luck.. Always check your exams carefully to see if the TA has made any mistakes.

8) I am generally a very curious person who doesn't mind studying anything. But after studying something for a long time, I would also get bored and frustrated.. At those times, I would keep telling myself "STUDYING SHOULD BE ENJOYABLE. IT IS REALLY INTERESTING!" OK.. Maybe I was just a bit too crazy..I don't know. My point is that at times, it is important to motivate yourself and to keep remind yourself how interesting the topic is.

These are all I can think about it so far..If I remember more, I may add later.