Seeing what you were up to, and what you were excited enough to tweet about, can give you some helpful (and funny) perspective .TwitShift gives you a convenient way to follow your one-year-old self.
With a journal you can physically go back to the past and review what is going on with your life. Webapps like Memolane let you to log in and view your past online life. But TwitShift, from James Wheare takes your twitter stream (the last 3600 tweets due to an API limitation), feeds a private account from it, and lets you follow it from your own account, or even automatically retweet yourself from a year ago.
TwitShift is a free tool that requires creating a new Twitter account, and authorising with your regular personal account, to use.