I keep an old phone in the bathroom, and every morning I use it to file my weight and my peak flow (for asthma tracking) on a web page I host on my home server. The server just appends the numbers into two text files, and plots some nice curves. In case of errors or other problems, I can just go and edit those files. The basic tracker took about an afternoon to code, by hand, long before we had LLMs. I have a more advanced tracker system to remember all the craft beers I drink, that one has recently migrated to a sqlite backend, and the LLMs have helped me to add many more features. Some of my friends have wanted to use it too, one lasted a couple of months, the rest gave up within a week - it requires discipline which most people don't have - I wouldn't either, but being my own system I am more inclined to keep using it, and adding features.

My advice would be to find a way that minimizes the friction, and get it into your (morning?) routine. And keep the system simple to begin with.