I keep a record now, because I had the same problem SearchTrail described. I would change a title one day, adjust internal links the next, and update content later in the week, and when traffic moved I could not say which change mattered. A simple sheet fixed most of that, and I agree with Garlick that keeping the old version matters most. If a change hurts, I want to put the page back exactly as it was, not rebuild it from memory. I also agree with sharifawan and SEOMonster01 that a log on its own does not prove cause. That is why I now write down the rankings and clicks for the page before I change it, and what I expect the change to do. Without that baseline, the log only shows what happened, not whether it helped. On pages that already rank, I make one material change at a time and wait about two weeks before judging it, for the same reason sharifawan gave. On pages with little to lose, I batch changes, but I log the batch as one entry so I do not later pretend I tested each edit separately. The other habit that helped me is adding the same date as an annotation in analytics, so a later dip does not look unexplained when the answer was already in the sheet.
