Happiness is not found. It's not an object, rather a state of perception. The more you'll objectify and discretize happiness, the less likely you're to achieve it.
That being said, usually drugs.
On a serious note, two books helped me to understand this mystery a bit more
Zen Mind, beginner's mind by S. Suzuki
Flow: the psychology of optimal experience by Mihaly Csikszentmihalyi.
Ah, another non mainstream source of inspirational knowledge is the Blindboy Boatclub podcast. Over years he produced a lot of episodes on the subjects of mental health and experiences delivered in a very democratic, relatable way. Mixed with crazy hot takes, like how Ney York disco was the original punk for/by LGBT community, seasoned with a thickest Limerick accent and storytelling. Delicious.
I think your comment is the key. Many others tell what to do, but yours addresses the core in that you won't be happy unless you decide or allow yourself to be happy (perception).
I used to mock those people who would say things like "smile in the mirror and tell yourself that it's going to be a great day". Later in life, I figured out that that's what they needed to do, so good for them. For me, it's something else. I need to be around nature to ground my feelings. Other times, it's physical cardiac exertion, like a bike ride.
Medication can help if there's a real medical problem, like depression. Self medicating can be dangerous.