I know, I'd love to always get my workouts done before work, but having downstairs neighbors, sometimes it's way too early to be doing Cathe and not be evicted. So, my best advice is to make sure that you drink plenty of water all day, and that you have a snack BEFORE you leave work. Something around 200 calories, a mix of quality carb and protein. Think veggies and tofu, soy, chicken, etc. Or fruit and yogurt. Oatmeal made with milk and a few walnuts and berries thrown in.
Kashi makes a new make in the microwave hot grain/oatmeal cereal, comes in individual packets (vanilla and cinnamon are the two flavors). They each have 150 calories, 2g of fat, 26 carbs, 5 grams of fiber only 7 grams of sugar, and 8 grams of protein. Make w/ 1 half cup of soymilk or reg. milk (it calls for more liquid, but it's too soupy for me that way). Yummy, hot, quick. I like the Honey and Cinnamon better than the Vanilla. This way, you've had the snack, it's started to digest so your stomach is not too full and you are getting the energy from the food.
Hope this helps,
Mattea
I forgot to add, then you just MAKE yourself do it until it is a habit. Start with your favorite workouts, or ones that you perceive as being "easier." This will help get you into it