^ I was going to say this, too. I have a really hectic schedule, too, but the only time that it bothers me or feels too tiring/overwhelming is when I haven't gotten enough sleep... Then it's simply unbearable!

I guess it might be a bit of an obvious suggestion, heh, but sleep is THE most important thing to have enough energy for the day! Also, as far as snacks, my personal favorite pick-me-up is Naked juice (like Odwalla, but better, hehe! IMO at least). They are sooo yummy, and they even have flavors that are specifically mean to give you
energy! My favorite of those is Orange Mango Motion, but they're all amazing.
Okay, and I suppose normal foods can give you energy, too, LOL. I'd recommend fruit or nuts, or something with protein and/or complex carbs, like a slice of whole grain bread with one of the healthier brands of peanut butter (or soynut butter, mm!)... I also love pure fruit leather! Or those 90-calorie Special K cereal/granola bars; the strawberry ones are sooo good.
LOL this thread is really making me crave all of my favorite snacks, now!

I hope you find something good to energize you.