Do not grab the prepackaged 100 calorie packs or granola bars or a can of soup for your lunch. These options may be easy but do not base your diet around them. Ignoring for a moment all the info that says that processed stuff is unhealthy, or at a minimum fresh is better, eating packaging "stuff" is not a lifestyle...it is not maintainable. For instance, can you imagine everyday for the rest of your life eating your lunch out of a packet? That's what eating packaged stuff really boils down to.
Instead, most days, make yourself a nice lunch with multiple courses. Pack a salad or fresh veggies, homemade soup and a piece of fruit. You will never feel deprived, it is sustainable for the rest of your life, and it is like a treat compared to a baggies full of wheat thins for the same calories!!