One of the challenges I've encountered with all the workflow and prioritization techniques I've used and studied is around how to "merge" it into your life.
There are a several aspects that have been challenging to me:
Merging my new workflow into projects and activities already under way
Merging my new approach into effective interactions with others who aren't using this new workflow
Merging new (hopefully better) habits into my old habits and weeding out the old habits that are counterproductive
If I combine bits I've picked up from Covey, David Allen, and others, my key take-aways for how to manage this merge are:
Use your new method diligently for at least 21-30 days to help establish it as a habit.
Make your new systems and associated commitments visible, if you can - for example, let your family and at least some of your co-workers know what you're up to (and why you might be acting funny).
If you want to go a step further, find a "workout partner" that will take on the new system with you.
Keep the system as simple as possible (or as complicated as necessary, but no more than that) so you don't give it up because it's too hard to maintain.
Begin with a clear "short list" of things you want out of the new system - whether that's better life balance, improved productivity, increased focus, better results, more meaning in your life, etc. - and track progress against that short list.
Keep track of the "wins" as you go - they will help you keep going (I've heard that every time you play golf, there usually at least one shot you make that gets you back out on the course the next time - look for those shots in your life, as well).
Share what you learn with others. This has a couple of benefits - you get more moral support, and by teaching others you are compelled towards mastery of the topic.
If you have problems, don't give up. Get back on your program and spend some time reflecting on why you lost momentum, and what you can do to tweak (or trim) your system to make it less likely you'll get stalled again. This is "Weekly Review" time for GTD, and "Sharpen the Saw" time for Covey-ites.
My list is just scratching the surface - what have you learned?
The bottom line is that all of this is worth it. A friend of mine this week reminded me of a verse from Proverbs: "You use steel to sharpen steel; and one friend sharpens another." - I think it's a good symbol for how we need to find the right ways to improve ourselves, and our friends can help.
And you can always hope that you're the friend that your friends turn to when they need sharpening.