To cope with the stress of grad school, I follow an extremely strict workout/diet schedule... I feel like it's the one thing I have complete control over. Plus, the endorphins put me in a great mood. I spend a lot of money on food because I eat a lot of fresh fruits and veggies, but it's worth it!
Breakfast: Half cup oats w/a little bit of honey and cinnamon, fruit smoothie (I bought a personal blender and smoothies = awesome meal replacement. Usually I throw in a banana, some frozen berries, half cup fat free yogurt, skim milk, honey, cinnamon. You can experiment for days with these things.)
Lunch: salad concoction, just whatever I have in the fridge. Peppers, red onion, beans, corn, gouda, avocado, and some balsamic vinegar.
Dinner: smoothie, sauteed veggies, approx 4 oz lean meat
Snacks: fruit (usually grapefruit because it's filling), nuts, etc.
Once or twice a month I'll allow myself some indulgent dessert or a hamburger or something. But I'm training for a half marathon now so I pretty much stick to the above.