Okay, I will give a story. I came at this whole subject from the opposite side.
I have been practicing Yoga since 1991. I have been teaching Yoga since 1998. In college I was a Classical Studies/Comparitive Religion double major. I have been studying ancient texts from India since around 1984. A lot of them are about subjects pretty related to mindfulness. A large part of what, even the over simplified, physical practice of yoga is about is mindfulness. You do these odd things with your body and your breath and you try to be aware of how they affect you.
As a kid I played ping pong, really once in a while but, sort of, as often as possible. I played with recreational players. All of them were kids who played tennis. None of us used backspin at all. There was a period of 3 months after college and in between jobs where I played at a TT club and mostly used the robot because I was not really good enough to play with anyone from the club.
In 2009 I saw people playing TT at these outdoor tables that were near a place were I taught Yoga. I started playing. I probably would not have kept playing if it was not for this next detail. I noticed when playing, there were guys who I would play that I totally thought I was better than who I would lose to and it really got under my skin. It got me upset. It got me angry.
To me this was interesting. I know, I am a strange character. But at the time there were very few things in my life that got me angry. My parents at the time could do it once in a while but rarely. The only person who could really make me see red and become stark raving mad was my wife.
So, strange character that I am, I thought, this is a good place to try and observe that anger and how and why it comes up and what it is really about. You know.....that is actually part of what you are calling mindfulness. Seeing that process of where the anger starts coming up and what it is actually about: that would be a mindfulness practice used for a specific purpose.
For me, in table tennis, it was about a feeling of not being in control. And playing these annoying jokers who could not hit a proper drive, were clumsy and could not take a decent swing at the ball, but seeing them beat me by pushing, because they kept me from playing the game I wanted,
made me feel like I didn't have control. I hated that. 
LOL.
At a certain point I realized these guys, at that time, were better at something than I was and if I let go of trying to be in control I would be able to observe the situation better and the frustration and anger would not come up.
I would observe the same stimulation and have a different response to NOT BEING IN CONTROL.
Well, of course, over time learning
1) how to play a push and chop game was essential to starting to play even with, or better than, these defensive types.
2) learning how to loop and particularly how to loop backspin allowed me to only play a push game if I actually wanted to.
But that initial realization that what actually got me frustrated and angry was not being in control rather than something else, really was interesting.
These days, even when my wife is freaking out and out of her gourd, I can't remember the last time I actually got angry when she was freaking out and trying to push my buttons.
What does all this have to do with mindfulness and table tennis. At 3-3, I will be creative and try stuff and I won't get fussed if it does or does not work and will be focused for the next point. At 9-9 I will not only be calmer than my opponent, even if he is 200-300 points higher than I am, I will be able to draw on the creative stuff I tried at 3-3 and 4-4 to use tactics that will work better on the opponent at 9-9 than I would have had access to if I had been less relaxed and less focused on the process: in other words, if I had been more focused on winning points than playing the points I would have less in my bag of tricks to draw from. And what works for easy points at 3-3 often doesn't at 9-9 because, at that point in the game, the other player is prepared for that.
It also means that if I am faced with a difficult shot and I have a choice between an easy, shot that will give the opponent the advantage or a difficult shot that could win the point, I WILL NOT BE THINKING TO PLAY SAFE. I will go for the shot and because I have done that as much as I have, I will have a decently high chance at making that shot. Even if my opponent is a better player than I am.
So the real question in adding mindfulness to practice is: can you still be motivated to play if you are playing for the process rather than the results you are hoping for.
Being able to shut the mind off in a certain way, but keep focused and observe your play in the situation and go for your shots without though of the score once you are in the rally, so you are open to make those split second decisions, can really have its benefits in playing a match, right now, today. But it also can help you develop a mindset for developing technique and growing as a player.
So the question is, how do you become unattached to the results and progress while playing and yet still keep the focus and the drive that helps you progress.
