Make brief notes about training, recovery, nutrition, etc as this can be a great form of feedback. It could be an invaluable source of information for future seasons.
Here's 10 reasons why you need to be keeping a training diary:
Identify what it takes to be really fast
Correct Performance Slumps
Give your coach what they need
Plan to get better
For more information on any of the above factors please let us know and we will be more than happy to answer.