Overestimation

I think of myself as able to do a NYT crossword on line with 5 minutes added per day, so the Monday I would finish in 5 minutes, the Tuesday in 10, etc... But if I look at my stats, I find that the Monday actually takes me nearly 9, the Tuesday 16, the Wed. a little over 16, the Thursday 34, the Friday 42, and the the Saturday an hour. So I am really confusing my average times with my best ones. This means that there is a cognitive distortion at work that clouds my clear conception of my abilities.