Now I am guilty of this for sure. When I was younger I felt myself as skinny and weak ( now I am just weak). So I tried to push more and more and eat more and then look at my other friends and say "look at me muscles, I'm so strong", this was never the case and was just the way my eyes and mind decided to see this. The problem here is what I perceived as skinny or big, muscles or fat and overall what I was happy with. If you are never going to be happy with your body then your body will continually fluctuate and you will try to be something you are not.
I'm not saying don't go to the gym or don't do exercise; but don't act like you are the "dogs bollocks" for lifting some weights. Everyone should be doing exercise anyway and it is important to do what is right for you. If you are constantly comparing then you will never win, as once you reach one goal there will be another right in front of you. I have said this before and will say it many more times - Relax, eat what you want and exercise when you want- do what makes you happy and don't go extreme.
FINALLY- Don't think you are better than anyone just because you went to the gym, or that you ran at lunch. Don't do it for anyone else, just do it for you.
( I should put that slogan on a t-shirt)