I find that "happiness," such as it is, comes from an active mind. If you always have a project, that you enjoy to work on, to improve, to engage with, to think about, then you are likely to be happier.

You can have everything, but if you haven't thought about something new in the day, the feeling of repeating yesterday wears on you. You feel the stagnation.

I think a happy life is trying to reach out and achieve something, learn something, improve in some way, for yourself, and even better, for someone else, every single day.

Cheers. :)