Hey - you're NOT a failure! You're still concerned with what you're eating and getting healthier, so that right there eliminates the failure thoughts!
Look at the next meal and then the one after that, and the next time you can choose to be more active, let every success build upon the previous one. Don't wait to have a "perfect" week to feel good about something ... those weeks are few and far between for everyone. But really take pride in the small successes that make up our days.
Can you bring in a bag of fruit - things you like, maybe not necessarily the standard oranges/apples/bananas, but include those if you can - and start with a full fruit bowl on your desk on Monday and aim to have it emptied by Friday when you leave? Add whatever fruits you want - grapes, kiwi, nectarines, etc.
Break up your goals into a LOT of mini goals - then you're still feeling successful as you tick off the "I DID IT" every few weeks. Don't have all of them be weight-related - make some activity-related so you're in COMPLETE control of at least a few
Focus on healthy marketing - that will make meal prep so much easier and less stressful for you. I'm one who uses very few processed foods, so I'm in control of what we eat, but it also means that nearly everything needs to be prepped in advance. Do you have the time to prep main dishes every few days or on the weekend, so you're not time-crunched when you get home from work?
WHY do you want to lose weight? Write down EVERY reason you can think of - from the healthy-lofty thoughts we say/feel to the vain ones
... look at this list often and keep reminding yourself why you don't need to drive thru anywhere ... why cake is not your true choice...why - whatever.
A couple of things I picked up from the Beck's Diet Solution book that I especially liked were to say So What - (as in, someone brought in coffee cake. ... so what? ... I don't need it, so what if it's there) ... as well as just saying Not a choice (it's not something I'm going to give into now) ... i know i've altered these to MY thought process, but it works for me. And finally, give yourself CREDIT for good choices, good thoughts you have every single day. ... What have you done well today? What did you pass up? What did you bring that was healthy? Did you start out with a good breakfast? Give yourself credit for that.
You can do this - one choice at a time. One meal, one hour, one choice, one day, at a time. Build upon your successes and lean on those for support who will support you!!
Being overweight is hard ... losing weight is hard ... maintaining your weight is hard... you have to pick your hard.