Don't bother managing your time. Manage your focus. We use pomodoros to sharply focus on achieving a goal every 25 minutes. If you focus on the activity you'll just wheel-spin and dig a hole. So focus on the goal - what you want to achieve.
To really focus you need clarity about what you're aiming to achieve. So have a really concise and expressive way to define the successful outcome (be it an acceptance test, a vertical slice, or whatever).
Finally, getting stuff done is one thing. Getting the right stuff done is even better. So figure out what's important and focus only on that. Duh!