Best is to not "grade" any player and play them as equals. Once you are 2 games up you can always "ease up" on them.
This "easing up" doesn't work for me, or at least sometimes. Often when I say to myself I can play this shot slower (typically on shots where I have advantage and should get the point, or have more adv.), I miss more often than when I play with full commitment. So I am trying not to do that. Also this "easing up", in match, I lead 7:1 in 1st set in training match, I say to myself, OK I'll slow down a bit, and managed to lose the set. Of course sometimes it does work, when you lead 2:0 as you say, and relax even more, it just continues (not that it would matter that much, but it does). So these seems to be 2 different "easing ups" and I don't know what is the difference
Related is the observation, that when a clear defined thought enters my head, like "now I want to place it left", or like "good now I have a lot of time for the ball", I almost always miss. Or it feels so. So I am trying to not think, or somehow think 1 thing
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When I play a lower level player, I find myself far more tentative. I feel afraid to hit my best shots and just try to stay in the rally. I often pull my shots back at the last moment, and all my shots are just off. I make more errors, and it just feels like I'm stuttering. Why is this? It seems more of a mental issue.
Good news is, that when you are capable of identifying it, and describing it - like you just did - you already have the key for solving it. Of course it also applies to me. I have also described something, above, and I still don't know the "mechanism" behind it. WHY that "easing up" doesn't work? WHY not thinking works better? Someone else knows. And what is clear to me is not clear to you and vice versa. So in your particular case. It's a matter of priorities. First you need to realize all this, really all of it, doesn't matter much. Second is that you want to feel good. The next day, what do you remember from the training? That you lost the match, or that you played ugly out of position not low enough shots? Which of those makes you feel worse? Once you set that, the question disappears.