You can scream and rage and cry till your heart bursts. God may not respond, but He is listening. He can handle it. He knows what you are going through. Eventually, you may be given wisdom. Then your eyes will see, and you will understand your error. When you apologize, you will be given peace.
This is the biggest life lesson I have learned.
Other, more trivial stuff...
If someone tells you to take X amount of motion sickness pills because it will give you an acid-like trip - don't do it. You'll get the acid trip...and will wonder the rest of the night if you will die from a heart attack.
Don't empty your heart to a female you are not interested in being with. You'll have a hard time getting rid of her.
Do not drive when you are sleepy or under the influence.
If your car is spitting black soot, you should probably check your oil.
Don't get addicted to things that harm you.
Certain woman scorned are living hell. Do not expect morality from her. Do not expect her to do the right thing. Expect her to use whatever influence she has and manipulate whoever she thinks she can to bring you the most harm she can muster.
It's better to take a risk than regret a squandered opportunity.