There are a lot of great workbooks out there. especially for those about CBT. I recently have been finding it really helpful to monitor my mood with a log - specifically how I have reacted to situations and events as they come up. The second log I keep is an activity prediction long. I make note of how much I think I will enjoy an activity before I undertake it, then mark down the actual enjoyment after. Both logs have been extremely helpful in my seeing how easily I am affected by experience; in particular how negativity and thoughts run the course of my life. As a result I am trying to work on changing those negative thoughts. This is what CBT is all about.