I hear from people every day who are frustrated that they have what they think are “setbacks” in their quest for happiness. You are not supposed to be happy all the time! It is impossible. The goal to work towards is to be happy at your core — to know that once the doldrums pass, you will return to your baseline of happiness.
If you have children, think of happiness the way you think of loving your kids: the love is always there, and it never wavers, but boy, there sure are times when you’re not feeling it, right? That’s the same with your happiness — you know it’s there, even when you don’t feel it.
Appreciate the sadness when it comes and when it passes, and know that it will never defeat you, because you are HAPPY.