I wouldn't worry too much about the "cheating" like the others said...but moreso the peer pressure factor...don't let THAT be your reason for cheating...
And don't think of it as "cheating"...cheating, by definition, is a negative thing...if you are following whatever diet/training schedule you set for yourself, and you PLAN on giving yourself something that strays from that schedule (because you believe you earned it) think of it as a treat instead...then you didn't do anything "wrong" and you won't have to beat yourself up over it
The difference is planning on something vs giving in to some kind of external force...the latter being why you are pissed at yourself
What happens here, stays here