I think one of the keys to keeping your diet on track is to make your own meals as often as possible. I love to go out with my friends or the BF for a few dinners throughout the week so I make sure to make my own breakfast and lunch as often as I can. Work for me starts at 6:30 which means that I have become really good at being able to pack breakfast and lunch the night before so I can quickly grab it in the morning. Being "too busy" really isn't an excuse, packing my breakfast and lunch usually takes me about 5 minutes each night, the key is having your fridge and cupboards stocked with healthy and tasty foods.
Here is a look as my usual lunches: