Stop making excuses to avoid working out. If you really are busy, set up a schedule where you can exercise sometime during the week and stick to it. Even 10 minutes is better than nothing at all. You should see that this won't interfere with your schedule and that you can keep your productivity levels exactly the same.
When trying to lose weight, it always helps if you are in a good mood. Being in a bad mood or suffering a bout of depression will throw off your sleep patterns, cause you to eat for emotional reasons, and ultimately deter you from exercising properly. Make sure that you're avoiding stress and staying in the mood to diet.