Do not let what you cannot do interfere with what you can do.
Happiness comes from understanding one basic principle. Some things are within our control and some things are not. Our opinions, ambitions, desires, and aversions are in our control. We can change the contents of our inner character. Our body, wealth, fame, and social status are not in our control. They are external to us and not our concern.
There is only one way to happiness and that is to cease worrying about things which are beyond the power or our will.