It’s worth thinking about how we measure how “good” a life is and if that is superficial and too much influenced by fashion. For example the cliche is go travelling or get rich starting a business. “I raised kids” doesn’t have the same boastworthyness in a lot of circles, but arguably it’s more interesting. Or maybe not. What’s the life well lived metric?
For me? I wish I was happy. And I think some hard-to-treat mental illness is preventing my day-to-day happiness. When I feel envious of others, it's not only that they're rich and they travel a lot. They also have friends. They might even have a family they care about. They have hobbies and they have _something_ to do. A lot of them say they have problems with mental health, but you can't film a year-long depressive…
IMHO, this is a mistake, if not _the_ mistake.
I feel like i've been in your shoes, in a past life. I've come to believe that happiness is like the horizon, or the sunset. It's a fuzzy concept, which disappears if you go too close to it.
The horizon is not a place, and the sunset is not a moment. They are aggregate phenomena. You can't set them as targets, because they don't exist physically. You can observe them as composite entities, emerging in the right context.
Such is happiness. You can't set it as an objective, because it doesn't exist. And chasing it directly will only cause you suffering. Instead, try to set smaller goals, and let it emerge on its own.
Take care of your physical health. Take care of your relationships. Allocate time, not much, but regularly, for activities that you like (hobbies). Widen your intellectual horizons, e.g. by reading or listening to diverse people. Get better at what you do professionally. Try to find some form of meditation that works for you. Occasionally, try writing long, thoughtful comments on forums :)
Try to do these without looking too far into it; just trust the process. And at some point, you'll have the revelation "man, it's been quite some time since i felt unhappy!"