Lessons

Moderation.
Take the views of a normal person into account. Look at yourself from his eyes.
Be humble. Don't brag about yourself.
Be pleasant, even with those you disagree. In fact, more pleasant and at your best behavior with those you disagree. Show them genuine respect.
Be conciliatory.
Don't be condescending. Never. Never. The quickest way to make enemies is to be condescending.
Don't feign affection. Don't feign anything.
Be yourself but pleasant. Learn from others. Copy Obama.
Above all. Be loving. Don't ever be cynical or evil. Keep love alive at all times. Love and love. Be like Christ. Yet never be naive for there's evil in this world. Evil comes from selfishness. Yes, selfishness is the root of all evils. It's putting oneself above everybody else in the pursuit of biological and emotional needs. Stay away from selfish people. Even Buddha said so.
Fight fair. Don't hit below the belt. Better to avoid fighting. Life of fighters is short.
Be peaceful.
Don't be presumptuous. Don't tell people that you know they feel and think. It's an insult to others when you act like you're a mind reader. Nobody is. The human animal is unpredictable and inconsistent.