The less you expect of people, the happier you'll be
In order to really grow as an individual, you have to accept that no matter what people do to you -- and no matter how you expect them to think or act -- people are who they are.
The less you expect from someone, the less you can be hurt by them. The higher your expectations, the greater the potential for heartbreak and disappointment.
Come to terms with the fact that people -- even some of your closest friends and relatives -- will do things that will leave you scratching your head sometimes. Human beings are unpredictable, rash, and irrational. Just when you think you've got them figured out, they surprise you yet again.
Never rely on people for your happiness. You have to be happy with yourself -- first and foremost. Other people should merely enhance your life, not complete it.
As much as you may desire for people to think or behave a certain way -- because, in your view, it's the fair and right thing to do -- they may not see it that way.
At the end of the day, people tend to have their best interest at heart -- all the more reason for you to do the same. Focus on what you love. Embrace what makes you happy.