We fail to be happy because we are not satisfied with what we have.
So here are a few satisfaction guidelines:
1. Do not hold on to something that would never be yours.
2. Do not fight for someone not worth fighting for.
3. Do not cry for something lost, gone, and inevitable.
4. Appreciate what you have and be thankful for whatever things people give you.
Happiness is a mere construct of the mind. Everyone can be happy as long as they really want to.