Based on similar things he's said in many previous interviews, I think you should read "success in life" as "happiness in life", etc: read the quote as something like: A person’s happiness in life is determined by having a high minimum, not a high maximum. If you enjoy something a lot but there are other things which make you miserable, the latter will hold you back. But if almost everything is enjoyable (or at least tolerable) to you, then you’ve got a good life. — see the example from the article where he got uniforms to make toilet-cleaning more fun.