A few thingsoccur to me.

1. “Don`t sweat the small stuff”.

I spent too much time in my 30s worrying about trivia, or things I couldn`t influence anyway. I`m just not going to do this anymore.

2. God does not exist. Meaning in life comes from human relationships. I wasted a lot of time on the idea that God might exist.

3. Some people- a small minority – are bullies. You have to be prepared to hurt them.

4. Don`t make yourself into you own enemy. Accept you limitations. I used to punish myself a lot, for things which were inconsequential. And the self-punichment had not positive effects.