A training log that tells you something useful
A log can be a few lines in a notebook. It becomes useful when it helps you remember what you did, notice patterns and explain a question to your coach without relying on the feeling of the most recent session.

Record the same essentials
Use a consistent format: date, session focus, exercise or skill, planned work and completed work. Add a short note about effort in your own words. If your coach uses a particular scale, learn what it means before applying it. Numbers collected inconsistently can look precise while telling you very little.
Describe context without judging it
A rushed lunch, a poor night of sleep or an unfamiliar setup may help explain why a session felt different. Record the observation plainly. The note is not an excuse or a diagnosis. Avoid comparing a tired day with someone else’s highlight reel; your record is there to support decisions about your own routine.
Review before changing the plan
Read several entries together with your coach rather than reacting to one difficult day. Look for questions: does the warm-up feel rushed, or is one movement unclear? Agree changes within the programme’s boundaries. Keep the original entries when you make an adjustment so you can see what changed, why it changed and whether the new approach is easier to follow.