I think its different for everyone. Once I set my mind on things other peoples actions have little influence. I'v had ( and continue to) people eating junk in my office all day long, even goading me to eat piza and buns etc.
It never bothered me enough to break and do it, and now iv been on this road for 4 months now I'm simply not interested in junk. I could bath in Pizza and coke and not touch the stuff. I look at it as poison now.
Take a look at the fat people stuffing their face..do you really want to be like that and have all the future health issues to go with it?
Make your lunch at home and take it to work..simples.
Make a stand and be strong..rise above the SAD diet that is messing people up.
I have loads of like pages on face book that post inspirational images and quotes all the time..all fitness pages and workout stuff. They work for me. Some of the quotes really hit home..my fav is...
If you want something bad enough you will find a way..
If you don't, you will find and excuse..