In retrospect, I think this was the best advice that my graduate advisor gave me. I had just told him that my boyfriend - who was a graduate student in the same lab - and I were having a serious relationship, and one of the first things he said was: "Always remember that it isn't a competition". For years I have wondered how something that is so measurable in terms of papers, impact factors, grant money, etc can NOT be a competition, but now I think I understand. If you're constantly focused on competing, especially with your spouse, it will take away the fun and the joy of science. If you see it as a competition, you won't help your spouse with things, like thinking about experiments, or proofreading their grant. And if you see it as a competition, quitting academia means losing the competition, instead of gaining a new job. The fact that academia is so competitive makes the "two body problem" even more of a problem, because how can you be happy for someone if they are also your competition?
So I'm very glad my graduate advisor gave me this advise, even though it took me nearly seven years to understand its importance.