Is life really all about enjoying yourself and having fun?

Many eventually arrive at the conclusion that life is about enjoying yourself and having fun. "Enjoy whatever you want as long as it's not hurting others." This is a nice idea and I do mostly agree with it, but it tends to seem a little empty after awhile. Essentially when you refer to fun you're referring to dopamine in the brain being released. If all you want to do is have fun without hurting others this sometimes leads to things like drug use, self-pleasure, etc. You're not hurting anyone, you might be hurting yourself a bit physically and socially, but you're still living by the code of "life is about pleasure." At that point is this still the best accepted answer to the question why are we here? When we picture having fun we might want to imagine relaxing on a beach with friends and family playing volleyball or something, but that's not always how things end up. If you want a direct tap to pleasure it often comes via questionable methods, but comes nonetheless. So is there some kind of qualification to the pleasure you seek? Is there a more appropriate method to seeking the pleasure when trying to live life to the fullest? I don't see how there would be, but something about injecting the pleasure right into your vein doesn't seem entirely right either.

Then there's the question, how does our status on this planet affect our "purpose"? If we were thrown back into the stone age, would people still consider our main goal to have fun? I think it'd still be a little important, but it would be secondary to survival. So how can that be? How can our purpose in life change based on our circumstances? Is our primary reason to live still simply to live with having fun as a little extra credit project? I think that might be the case but if so how important of a goal could it really be?