If a person plays game after game of "fast" chess without trying to really learn from mistakes, then don't be surprised if they keeping making the same mistakes again. I have been playing slow chess lately, and I can try to understand on some level what I am doing with my choices from moving to specific squares. I want to take the learning in into future games, and with slow and contemplative play I have a better chance.
For instance, one of my games against Luigi. . . I saw where I needed to have taken a file with my remaining rook; however, I wish I had seen it ahead of time instead of simply in time. My opponent had a chance to take it , but apparently did not see it.
Lastly, don't expect to see everything mistaken all at once. If you can take one thing from one game into the future, then you have succeeded.