For me, 2012 was a year marked by a cycle between periods a extremely high activity and complete burnout. I now believe you don't actually gain anything by working in this manner because the high activity and low activity periods average out to be the same amount of work when compared to simply working at a realistic pace. I'm normally not big on making New Year's Resolutions, but it just so happens that the holiday break at the end of the year gave me just enough time to catch up and reset my schedule. For 2013, I'm pledging to stick to a sustainable schedule that still meets my goals and allocates my time based on what I value.
Getting Things Done is a great system for tracking and prioritizing, but it leaves it up to you to determine when you're actually going to do things. An experiment I've been trying for the last week is to schedule blocks of time to work on certain categories of tasks. So far it's been working out great!
I've been using an app called Daily Routine to schedule these blocks on different days. I have to say that the UI is actually a bit superfluous and difficult to use, but once you get it set up it works pretty well. Essentially it's a calendar, but it's a second calendar that I treat differently. My main calendar is for appointments. Daily Routine contains blocks of categories of activities (e.g., programming, cleaning, etc) that I treat as an advisory schedule which I try my best to stick to.
What I like about scheduled category blocks is that it means I'll at least try to get 8 hours of sleep. Previously, I would wake up at 3am and think "Can't sleep? Why not do some programming?" Another benefit of the category blocks is that it balances what I value. A long time ago, I attempted to do this with a task app for PalmOS called Life Balance. The idea was that you would assign a category and relative effort to each task and it would show you two pie charts comparing desired vs actual balance of categories of what you value. The problem with this was that it's actually a lot of work to assign relative effort to every task. It also does not take into account the things you do but don't need to put in a task management app, like sleeping!