If you have a smartphone with GPS (or other way to track your miles as you go), I'd recommend using an app like RunKeeper or Cyclemeter. It sounds like you're tallying up your miles at the end of the year. I find it's much more motivating to see charts updated every ride showing me how many miles I've gone so far this week/month. This makes it obvious to me whether I'm slacking off one month and makes it easy for me to see how many miles I'm no pace to do for the year.