The most apparent one i remember was 3 seasons ago where i had trouble vs C- players, and all my old SC buds were C level, and i couldn't win vs him, few weeks ago we were equal in level (hi yaqoob). I got out by massing games any chance i could and without really noticing any chances, i managed to get C, and then eventually C+ just before the season ended...
Now i'm starting to notice again. I got C+ this season much faster, like i got it in the middle of the season. On my smurf account i got to rank C, then lost a lot of games and my minimum points was like 3200, now i managed to get it up to like 3500. I have no confidence right now considering i'm having trouble vs C- players, i can't imagine how much i'd get owned vs C+ players.
As of my recent games on Andromeda, i can notice my macro getting worse, and making the world's most horrible decisions that i think was the best at the time. I notice in TvP's im not paying attention to my units when i push out and they end up getting owned without siege. My surplus is going out of control in my TvZ and TvP. The only improvement i see is my TvT, and before my TvT sucked balls. Thats the only matchup i see some decent improvement in. I want to say im seeing improvements in my TvZ late game, but again thats late game vs only C- zergs, and i'm still having trouble but i can usually win TvZ"s if i can bring it to late game.
Waiting patiently for me to crawl out of the hole and be even stronger than before.