Food for Thought

My advisor has told me before: "If you spend all your time in graduate school comparing yourself to everyone else, you'll never get a job." This came as a result of my anxiety about several peers who've already been published (as 4th yr. PhD students). I've had my work solicited for publication before - a conference paper I presented was solicited by an editor of a good journal in my field - but I would've had to develop it further before it would be ready. I was willing to do this though. But, my advisor told me not to focus on that..not to get distracted away from my dissertation by things that ultimately wouldn't really do much to help my job efforts. The problem is, I still feel the competition. Nobody is doing anything to make me feel this way; it's just there. The fact that I'm aware of what my peers are working on - even if they're not in my area of study - makes me constantly self-conscious of the "best" factor. I want to be the best at what I do in this place at this time. Is that possible? Is it a juvenile fantasy that doesn't (never?) existed in the first place? Am I immature for thinking in such terms?