There are plenty of reasons to write regularly (if only to chronicle your awesomeness), but keeping a lengthy journal is a daunting task. One Sentence Diary makes it simpler by keeping no more than 300 characters per day.
The service is incredibly simple to use. Once you sign up, you're given one text box per day. The entry is capped at 300 characters (or slightly more than two tweets), and you're not allowed to edit it after five minutes. If you're looking to start doing some self-analysis in the New Year without much fluff, it's hard to get simpler.