One HUGE thing I learned from being diligent about competing in tournaments was I found out how vital it is to refocus during a match.
I wrote about this before and I still think it's a huge, important thing (link here) to increasing your winning percentages.
And I experienced this just the other day in league playoffs.
Basically, a match can go by in a instant! And then afterwards, you think, "what happened? why did I lose?"
Although you should always evaluate your game and learn after each match - how about after you miss a few times you ask yourself those questions right then and there (what's going on, why am I missing?). Don't wait til after the match to finally realize why you were missing. Figure it out before the match is over so you can try to resolve it.
Probably over 200 times over ten years after a match, I realized, "oh crap I was nervous" or "dammit I wasn't staying down" or you were worried about someone watching so you felt funny and were concerned more about that than focusing on three-balls-ahead-shape.
After a match, it's TOO LATE. So the key is it REALIZE early that your game is off and to figure out why during the match so you can resolve it before the last ball falls and you lose.
Sucks to figure out later what was going on.
However obvious this sounds, it's really not. It's really about training yourself to recognize that something is off. As soon as you miss a few balls - what is different? Why am I missing? What am I thinking or doing? And then resolve it - right then and there - to give you a better chance at getting back into the match at hand.
So during league playoffs, my opponent ticked me off b/c she said we didn't need a ref even though I wanted one. It took me about 5 missed shots (in 8ball with a tough table, luckily) to realize I was missing because I was upset with her. And since I was upset with her, how can I possibly focus on pool? (multitasking is something our brain cannot do well - read another link here).
So, as soon as I realized what was going on in my mind and with my body being upset, I was able to refocus back on my fundamentals and not miss again to win for my team. Can you imagine if you were in a race to 5 or 7 of a match? Figuring out what is going on can easily get you back in the game even if your are down 0-2 or 0-3.
It's normal to get distracted at times, the key is getting you back on track as soon as possible.
I got lucky I had time to regroup. That's why it's important to really recognize right away that something is off so you can resolve it to give you a better chance of winning.