Mother Teresa

People are often unreasonable, illogical, and self-centered;
Forgive them anyway.

If you are kind, people may accuse you of selfish, ulterior motives;
Be kind anyway.

If you are successful, you will win some false friends and some true enemies;
Succeed anyway.

If you are honest and frank, people may cheat you;
Be honest and frank anyway.

What you spend years building, someone could destroy overnight;
Build anyway.

If you find serenity and happiness, they may be jealous;
Be happy anyway.

The good you do today, people will often forget tomorrow;
Do good anyway.

Give the world the best you have, and it may never be enough;
Give the world the best you've got anyway.

You see, in the final analysis, it is between you and God;
It was never between you and them anyway.
Attributed to Mother Teresa

And more wise advice here