The purpose of going to school is to learn; getting an A is the indicator of success (but can be falsely attained by cheating). The purpose of life is to grow; being happy with your life is an indicator that you're succeeding (but can be falsely attained by addictive behaviors and substances).
https://yourmeaninginlife.com/blog/happiness-without-growth-is-like-getting-an-a-without-learning
The problem with any behavior is whether someone unwillingly is harmed or pays the cost of another person’s behavior—not who benefits. Therefore, both selfishness and altruism can be bad if it someone else ends up being harmed or paying for it.
https://yourmeaninginlife.com/blog/non-consensual-harm-or-expense-vs-the-greater-good
You don't have to save the world; your life and world get better one day at a time with every constructive act you take.
https://yourmeaninginlife.com/blog/you-dont-have-to-save-the-world
You can always find a reason to complain, and you can always find a reason to be grateful. The former will lead to a miserable life; the latter will lead to a more pleasant life.
https://yourmeaninginlife.com/blog/it-will-always-be-something