Every reality has either of the two aspects: you can either change it or not.
If you can change it, tell the reality that you are more powerful than it.
If you cannot change it, tell the reality that you are more powerful than it: by not letting it take away your happiness.
The happiest of people are the ones who stay positive in every aspect of life. Positivity is a choice, not subject to circumstances outside you.
P.P.S.: Bonus point: If you choose positivity come what may, circumstances and people magically begin to be better.