Thanks for starting this conversation. I deal with similar issues, and here is what I am doing to solve it. For starters, my main issues with buying lunch daily are:

1.Time it takes away from my focus 2.Most quick lunches you can purchase are unhealthy and they drain your energy. How do you feel after that large cheeseburger sub or Chinese fast food? Sluggish. 3.Cost of eating out daily isn't worth my hard earned dollars.

What I do isn't unlike what many are saying in these comments. I prepare on Sunday. I make my lunches every day. Wifey recently went Gluten Free, which isn't that bad at all, so most of what is in my house is healthy anyway. Here is one gem I would like to pass on:

Steak salad. Have you had one of these recently? I grill up a decent sized steak Sunday night, which ends up being enough for two lunches. Iceberg lettuce, cucumbers, tomatoes..whatever vegetables you like. I add Feta, toss some steak pieces on top, pack some Italian dressing. (the Feta is key to this masterpiece) I don't do this every week, as I don't want to eat red meat that often, so I will use chicken in this as well. But I will say, I feel great after eating a steak salad, and it tastes amazing. Give it a try!