Yes, I think it's crazy to keep gym progress in an ongoing draft email. If you discard the draft, you lose everything. I frequently take notes by sending emails to myself (and replying to that email to add details), but I never leave it as a draft.
Entrepreneurship is a big focus for me right now, so here's what I log every day:
In the AM: (1) What are the current goals for different areas of my life and what does it mean I have to do today? (2) What are the biggest challenges I have with #1? What are the skills I wish I had right now which would have been really helpful? --> Those seem like good areas to research and read up on.
In the PM: (1) What are my accomplishments today? (2) What were my total # of productive hours? (3) What am I grateful for today?