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.