I have been prayer journaling for years. For some time, I actually used two separate journals, one for thoughts and ruminations and the other for prayers. Then, a few years ago, I combined the two, at first using a different color ink for prayer than for other entries. Then I shifted again, and began simply concluding my journal entries with my prayers (still in a different color).
This post (here) capsulizes why I so highly value my practice of prayer journaling.