There is an explanation for everything that happens, but that's not exactly the same as "a reason".
I do not think your (or anyone else's ) happiness is dependent on gods. Either they exist or they do not, but either way, they do not impact our lives directly.
You need to be a bit more proactive, figure out what would make you happier/more fulfilled, learn what it would take to make more of that happen, and get started.
Say more money, better mental health, more/better social interaction, etc would make you happier, all of those, while not guaranteed, are at least possible to achieve, fully or in part. But they all would take effort and study, they will not happen automatically.