St. Josemaria Escriva says:
The cheerfulness you should have is not the kind we might call physiological, that of a healthy animal, but a different, supernatural one, which comes from the abandonment of everything and yourself into the loving arms of our Father God.
I want you to be happy on earth. But you won’t be if you don’t lose that fear of suffering. For as long as we are “wayfarers, it is precisely in suffering that our happiness lies.
That was an eye-opener for me: Most of my unhappiness stems from the fact that I am too anxious to suffer or to make sacrifices. I’ve tried to avoid suffering at all costs, and in the end, the more I suffer from too much anxiety, the more I could not find joy in my life.