Overview
When you agree to do something today, you have to stick with it. It's not wise to commit yourself to doing something while simultaneously creating an escape plan. If you don't want to be involved, don't get involved. Calling in sick at the last minute is not the right way to remove yourself from a situation (unless you truly are sick, of course). This type of flakiness is not as harmless as it might seem. Honesty will help you avoid getting a bad reputation.