Here’s an interesting idea from Scott Young that may just help with your growing to-do list: Set up a Project Kill Day. In short, you schedule a distraction-free, off-site day to “kill” off one of your projects. Check out the entire post for his step-by-step guide.
Not sure which projects you have that merit an entire day? Try writing down the first client-related task you think of in the morning and the last one you think about before bed. If it is the same one for more than a day or two, kill it before it kills you!