My dad told me 4 things when I was young.
Son, life isn’t fair and the sooner you learn that the better off you’ll be.
People don’t care how you feel, they care what you think. (Wish that was still true)
Give a man $1.10 worth of effort for every dollar you’re paid, and you’ll never want for a job. (Not sure that’s still true)
Treat everyone you meet with the same respect you’d expect. They will soon show you if they deserve it, don’t deserve it or deserve more.
I think the most difficult lesson is, Life is not fair. Once you accept that, everything else should fall into place.