Have you ever written a letter to yourself? Why not try it out? Sometimes keeping a diary or journal can seem like a bit too much work, and we tend to forget to write in them after a while. It would be so nice to have a written record of the year's events and how you were feeling, though.
So if you do find it hard to keep a diary, perhaps write a letter at the beginning of the year to the you a year from now. Talk about the stand out happenings of the year before, lessons you've learned, things you've accomplished and how you are feeling. You could even write about your hopes and dreams for the year ahead.
Put the letter into an envelope and address it to yourself in a year from that day, and then pack it away somewhere special and perhaps note the day on a calendar as a reminder.
When the day arrives for you to open the letter, you could write a reply to the you of a year before, helping you to reflect on the year that has just passed. And then write another letter to your future self. I think it could be quite interesting and somewhat valuable.