I use a cheap paper calendar for this instead of another app. Each morning gets one letter - W if I walked, P if I hit protein, S if sleep was decent - and on Sunday I jot the seven-day weight average in the corner.
Looking at the weekly average, not the daily bounce, is what keeps me from panicking. My last three Sunday averages were 1.3, 1.1, and 1.5 lb down, which made me pause, so I started noting appetite and energy beside the number.
In the trials, early lss can be quicker than later loss, so I'm trying to read the trend rather than grade every morning. It's low-tech, visible, and easy to keep up.
Does anyone else use a paper system, or do you prefer a spreadsheet?