When has comparing yourself with someone else every really helped you??
Sure, in your head, it is nice to come out on the winning end of a comparison but honestly, if you are taking the time to compare, you are probably looking for justification of your actions or self in a situation where you are not sure if you are in the right.. So comparing doesn't really change things, it just focuses your attention away from an honest assessment of what is going on and lets you off the hook because you are not as bad as XYZ.
And if you end up on the losing end of a comparison? What then? Will it motivate me to work harder because I can't run a 5k as fast as So-and-so? Maybe, maybe not. But wouldn't my energy be better spent in the doing of what I am trying to accomplish?