> everything seems to indicate that there will always be something to improve, so if everyone was driven like this, nobody would be left to enjoy the fruits of these sacrifices, making them ultimately pointless.

I agree. But to me, this is not a dichotomy. As in, you don't have to choose between complete comfort (do your job and watch movies) and total sacrifice (devote all your time to a cause). You can have time for friends and hobbies and still do great good for your community and the larger society.