I firmly believe that happiness is a failed concept. It frames the fundamental emotion of joy as this attainable human state that we are supposed to be in. But joy, like all emotions, can only ever be temporary. If there is no joy, our lives will feel worthless and painful and we must do something about that. But just seeking joy, "happiness" or attempting to make it permanent is just as detrimental, as anybody who has suffered from addiction will know.

A much more useful word (in english) is content. You can be content with something, even if it makes you sad. When my grandfather died, I was sad and deeply heartbroken. I certainly wasn't happy, but i was content with how we said goodbye, how he was cared for in his last days, going out on his own terms.

ADHD and especially the medication made me realize how fickle our brain chemistry is. My meds go ham on my dopamine production/absorption and suddenly I'm doing good, finding some joy in my work, even if it bores me to death. Until it wears off and then sometimes I crash and feel sad, lonely and hopeless. But now that I am diagnosed and medicated, I am more content than I ever was because everyday i act instead of just being acted upon and it shows in all facettes of my life.

If you are rooted in a reality that you find fundamentally acceptable, that you are content with, you have a much better chance to endure the emotional storms. This is difficult and there is no guarantee. But it turns a non-existent emotional state into something that can be worked on, grappled with, and it is something that remains, regardless of how you feel in that very moment.