Because thinking determines life. It is a common habit to blame life upon the environment. Environment modifies life but does not govern life. The soul is stronger than its surroundings. The direction of a man's thought is always the decisive factor in his personality.
Every thought is a seed.
What your heart thinks is great, is great. The soul's emphasis is always right. The brain that bubbles with phrases has hard work to collect its thoughts. If everybody thought before they spoke, the silence would be deafening. If we are not ashamed to think it, we should not be ashamed to say it.