I'm not sure I've ever known and am not certain I will. I can be happy in a moment, but that goes away. Meds help me shrug it off, and I don't tend to dwell on existential shit like this for long, but like...I dunno that I was cut out for this world, yo.
Also this isn't a cry for help and im not particularly sad or upset right now, I was just walking one of the pups and thought to myself "if I can't be happy I'm gonna make sure these fuckers are."
For me happiness is cat shaped, having a small little kitten creature curl up on my chest with purs reverberating through my bones it felt like an entire lifetimes worth of anger and baggage just fell off. At that point I understood my newfound purpose as sentient chair for this fluffy critter