The advice proffered below is not all from firsthand experience; here & there it is drawn from my having a ringside seat at others' trials, tribulations & screwups.
Be careful of your thoughts, for thoughts influence your actions. Your actions in turn influence what other people may or may not do to you.
Those who marry for money will end up having to earn it.
Having loving relationships with one's family is all well & good as long as they are decent themselves & can support your efforts as well as you support theirs. If that is not the case, cut all ties to them. Family members are just human like the rest of the herd, & they can hurt you just as badly.
If you want to avoid being surprised, have low expectations where humans are concerned. You will seldom be proven wrong.
When you are young, set put to achieve your dreams & do not let anyone stand in your way. You won't live forever, you know.
You cannot fix other people's problems, so don't waste your time trying. Help others when you can, of course, but don't make their problems yours. You'll have enough trouble solving your own problems as it is.
Remember that when dealing with someone you do not know, it doesn't hurt to assume he is an enemy worthy of respect until he proves himself a friend worthy of affection.
Above all, always do your best to see things as they are, not as they ought to be.