I keep a running journal to manually record my route, distance, time, and notes on daily runs (or rests), with one entry for every day, whether I run or not. It started out as a Runner's World pre-formatted book that I'd bought at Smith's, but after a couple of years of those, I just started writing out the headings each time, always making sure to include some information on how the run went. This might be how I felt, or how the weather was that day. I paraphrase below from my journal entry for today.
Yesterday I received the Radgick Award for ultra-running from Bracknell Forest Runners. This was an incredibly validating and meaningful award to receive for me. It has a great deal of value in addition to that which I gained from completing Race to the Stones and Run to the Sea this year. That extra bit of recognition really helps, and its value goes way beyond the physical object. And it's not just about looking back.
I now have added inspiration about what went so well last year, and how to apply it to the coming one. I've identified 5 things that went well and that I plan to continue doing:
1. I listened to my body. I didn't run when I felt that doing so might result in injury or sickness.
2. I was consistent. Long (10, 12, 15, 18, 20+ miles) training runs occurred at least every other (if not every) week.
3. I let myself recover: 2 rest days per week
4. I did strength training (at the gym or at home): 2 times/week
5. I paid attention to eating enough and eating well before, during, and after running