Mindset is very important. I have a personal anecdote on this. I started wrestling in 4th grade, and built up my skills and confidence incrementally. It took a long time to have faith in my skills on the mat, and I wonder how many wrestling matches I lost over the years because I wrestled well known dudes and I let it get into my head that "I can't beat this guy, he's too good". But by the time I graduated HS I was an All State wrestler and owned a lot of big wins, even one over a national FS champ (albeit in a folk match). But there was this guy on my team who started wrestling as a freshman (when I was a sophomore). He had no idea he wasn't a good wrestler (he really wasn't that good), but the guy had an almost unbeatable mentality. He had a 27-3 record his first year, or something very near to that. Granted, that was the last year of Jr High back then, and against Jr High kids...but 27-3 in a first year is pretty damned impressive. The guy was a winner on the mat, somehow. His technique was rotten, but he was a great athlete and he thought he was going to destroy everybody on the mat. His success dropped a little in HS, but he was still winning 20 matches or more a year against just a few losses. I don't know how he did his Sr year, I'd graduated by then, but his Jr year he finished 5/6th at state. He didn't realize he was supposed to be struggling and just gave it all on the mat.
Mindset is very important.