A useful and very simple technique involves a timer. Set it on for 15 or 20 minutes and tackle a chore you’ve been postponing. When the timer goes off, you can stop, although once you start, you’ll probably want to get going and finish it.
Say "no"
Put yourself first. Sure you’d love to fill in for a coworker (again!) but if it means cutting into time you had already scheduled for an important personal task, think twice. Say “I’m sorry, I can’t. I already have plans for that day.” Do not excuse yourself and do not offer explanations. You have a right to say no.
Do two (or three or four) things at once
Remember about the phone conversation while sorting your mail? Find ways to make your time do double duty. Do crunches while watching your favorite sitcom. Write thank you notes while waiting for dinner to be ready.
With just a little organization, you could find that elusive 25th hour!