I know this may sound kind of lame, but I do a daily recap. It's a great way of "putting my brain to bed." You can do several interpretations of this, but I choose to pick five things I'm thankful for.
Example:
Today I'm thankful for:
1) String cheese
2) Free beer at [bar]
3) A good coaching session with [employee]
4) Killer workout
5) Finding really cheap gas
Sometimes I elaborate a little more, but you get the idea. I choose to do it as a "thankful for" exercise because it's more optimistic. I have a tendency to drag myself down near bedtime with the stress of everything that is coming in the next day or week etc. This exercise causes me to stop and reflect on the good stuff.
Another great way to do this, as it would relate to GTD, would be to do a hits and misses style recap. David Seah (The Printable C.E.O.,
http://www.davidseah.com) uses this method on a weekly basis to evaluate his productivity, but you could shorten it up and make it effective for the following day.
By making a short list of what went well and what didn't, in effect you are setting yourself up for success the next day. Once you have written it all out, it's just that..."out." You can give yourself permission to stop thinking about it. The other cool thing about this type of exercise is that by reviewing your own records, you can track patterns. For example, if one of your misses is that you were distracted and couldn't complete a specific task, you may find in reviewing your notes to yourself that this occurs every Thursday afternoon because you're thinking about your evening plans with your friends every week. You could then schedule short-burst tasks for that time of day rather than lengthy projects.

Wow, that ended up being a long post!