I used to lose to the same guy over and over, I can certainly say Tha I have better technique all around and understand better the game, in practice I used to beat him without any problem but in matches he used to always win.
In a tournament I was playing, one day I had to play in the QF against a tall guy, very intimidating but I was the better player, it was a two sets of 4 games with a match tie break if we tied at 1 set, I was 1 set ahead and serving 40-0 for the match, somehow I manged to lose that match, it was awful, the worst was that my daughter was watching me play, I ve never resented any loss until that day, I've always focused on anything I can learn from the loss, be it a good point, a nice shot or whatever positive, that loss brought me no positives at all, just shame.
After that match I decided to just focus in the point I'm about to play, not in the last point or the next one, just the one I'm playing, if I'm serving, I do a little ritual to focus and just think about the point I'm about to play, if I'm returning, same thing, I just touch my leh on the left side and prepare to return, I do this as a way to let my mind go of any intrusive thoughts, to let my subconscious self play the point and the conscious part to plot the tactics and above all, I convince myself that it doesn't matter if I lose as long as I play my best and not just try to not lose, I prefer losing a point going for my shots than losing it by being too careful and setting up the opponent for an easy shot.
Anyways, after that painful loss and the work on my focus I started winning against that guy I used to loss to sl the time, I got so hard for him that the last time we played like 6 months ago, I beat him in two matches we played back to back, 6-1, 6-2 and 6-4, 6-2, it was a bad loss for him because he used to beat me all the time and this couple of matches were like the 10th loss in a row for him against me, he told me as a joke that I didn't let him even think about winning, it was a good day for me and I called my wife to tell her, she immediately told me that I shouldn't have beat him like that or I'll risk he wouldn't want to play with me anymore, I told her I didn't though he would be like that and when I was in that position it motivated me to work harder on my game, lo and behold, she was totally right and that guy didn't even reply to my texts anymore, I won the match but lost my tennis buddy.
Rant over.