Insightful post from Dr. Drang:
This is an important point, especially if you're new to task management: it's a common belief that if you adopt a list-based approach to manage your tasks, that method can only work if you zealously update your lists every day.
I'm not here to tell you that you shouldn't keep your lists up to date, obviously there are advantages in a continuous and active GTD implementation, but please know that you can have great benefits from making lists of tasks even if you don't check and update them all the time.
Me too, but I know people who do just the opposite and that works magic for them. Just find what seems to fit you the best, be sure it's fast and unobtrusive and go for it.
The best solution for you might be pen and paper on the bedside table, it might be the preinstalled basic app on your phone, or maybe it will be Tasktic on all your mobile devices...
After a while you notice that you haven't had time to look at your lists in days? No problem, just bring them up to date and start over, maybe adjusting some details you think didn't help you being effective last time (don't have time to look at your list in the morning? try doing it last thing before leaving the office, etc...).
You won't form a habit in a day, but it's not worth it to give up a great organization method just because once in a while you find yourself temporarily abandoning it.