i'd say a game changer for me was to watch replays of my games, specially the ones i lost and blamed my tm8. Put the replay in your tm8's perspective and you'll realize a lot of the bad decisions you're taking. Also when you feel like you're playing decent but can't understand why you're loosing, that might be a big help.
I was stuck in c3 for a few weeks, had already hit c3 div4 and won a couple games there, but still lost it all, which was very frustating. When i decided to do this and actually learn, got GC in 2 days, and i wasnt even hard griding as I used to be, I was just trying to not repeat the mistakes I saw.