A few years ago I flossed for a whole January, but then became complacent and stopped. It might have been an altogether too hard NYR for me, so this year I have one good idea and a firm intent to keep it:
I have a few reasons for this. I was raised to believe that if I visit a doctor more than once a year, I must be a hypochondriac. So I just didn't. Plus, since I almost never see any doctors, I don't really know what is worrisome and what is normal, I just used to ignore anything happening with my body. This is also an excercise in trust. I know I can't really trust myself in the matter of my own health, so I will consciously put trust in other people intead of waving away their good advice.
The new year is a popular Schelling point to make changes to your activities, habits, and/or thought processes. This is often done via the New Year's Resolution. One standard piece of advice for NYRs is to make them achievable, since they are often too ambitious and people end up giving up and potentially falling victim to the what-the-hell effect.
Wikipedia has a nice list of popular NYRs. For ideas from other LW contributors, here are some previous NYRs discussed on LW:
(If one of these were from you, perhaps you'd like to discuss whether they were successful or not?)
In the spirit of collaboration, I propose that we discuss any NYRs we have made or are thinking of making for 2015 in this thread.