I've been bringing my food to work to handle anythign from a regular day to being gone from 5 am (AM gym / competition prep) until 10 pm (work + PM gym + traffic). I carry a softside cooler w/ a couple ice packs and tupperware w/ each meal. My meals are generally 3-4 protein + veggie meals - e.g. chicke + broccoli or chicken + salad, a couple emergency meals of nuts (e.g. almonds or peanuts), an extra container of already cooked sweet potatos.
I cook chicken & stuff 2-3 x/week, plan ahead what I'm supposed to eat & just prep it the night before. Takes a little bit to get into the swing of how to pack stuff & get it into the cooler, but once you find what works for you, it becomes mindless. Don't forget to pack the forks, spoons, napkins or whatever else you need.