your mental state is extremely important when it comes to accurately judging your level of skill. Cura can tell you, for example, that I've been raging quite a lot lately about technical errors during my practice with him. I know this isn't good for my progress at all, and over the next couple months I'm going to work on that.
I had some issues during the tournament as well. For example, during my match with Moss in game 3. As the time was running down, the game quickly turned into hit and run, as anyone watching the match could tell you, and it started to provoke some interesting commentary behind us. I paid a bit too much attention to the talk (at one point I think I jabbed him to get the lead and ran to the opposite ledge ASAP, someone laughed at it behind me and I even cracked a smile lol) and I feel like I lost some mental focus in the process. Definitely not johning, because this is something completely under my control and I need to get rid of it.
My second issue is mental endurance I guess. After losing that super long set to Moss I was pretty drained mentally, and discouraged. At this point TommyGreenShirt would probably beat me regardless but I feel like I could have done a lot better than I did, and threw out a lot of desperation moves that got me punished hard. Now that I think of it internal frustration is another major issue of mine.
TL;DR your mental state is just as important as any other part of your game.