When reading tactics puzzle books, I now write down all my answers:

If I think a problem was easy, I'm finding 10% of the time I still got it wrong. If I thought it was difficult but I think I solved it, then 1/3 of the time I got it wrong. So instead of whizzing through a book thinking I'm learning new patterns, I may have been reinforcing bad ones. So now I'm redoing them all and writing them all down and checking. A few of my answers actually are alternative lines, but catching these kind of errors is good. Next time I do them it will be interesting to see my gut response.

As for the ones I knew I could not solve, I spend only 5 minutes trying. Then I've learned if I just try to memorize the answer, I often can't solve it the second time either. In order to remember the new pattern, I have to break it apart and asky myself what motifs are in each move and how much tolerance the position has to changes in order for the combination to still work. I then look at the puzzle and figure out what would have given it away. After all that, I get it right the next time I see it.

I've also noticed that my web browser does not spell check my posts on chess.com, so often I have to copy paste words into a search engine to find the correct spelling. Years of getting my spelling corrected has not helped me at all. In order to learn them correctly, you need to look and see if you just made a typo or an actual spelling error. If an actually spelling error, you need to write that word down on a list and review it a few times over a week, or it won't stay in memory. I wonder if studying so much chess is making my other abilities atrophy. At least now I'm less judgemental of other people who make spelling mistakes.