Mid match meltdowns (magnitude of them will vary) can have numerous sources - but if we exclude things like fatigue, hunger, dehydration, etc. and focus only on the mental aspects of them, what we find most often is stress from doubt and lack of confidence or a few bad recent errors insidiously creeping in and getting the better of us. The reality is that in most cases, our bodies physically/reflexively know what to do, and our challenge is really to get our brain out of the way and let the body do its thing. In order to do that, you have to quiet the paniced mind. This is about the "fight or flight" reflex (there are some other hormonal aspects to it as well - cortisol, etc.).
Anyway, it boils down to this: your non-executive (non cortex) brain function cannot differentiate very well between the stress of a second serve at Ad-out and a saber toothed tiger bearing down on you... so when it kicks in, your body goes into this fight or flight mode, and one of the first things that happens with that fight or flight mode is the executive functions (complex, higher ordered cognition, etc.) of your brain more or less shut down... further, fine motor control is also hindered greatly in "fight or flight mode". If you think about it, this makes sense for when a saber toothed tiger is bearing down on you - you don't need to be thinking about what you're going to do about your henpecking wife, or how you're going to get Larry the flintknapper to make you a new knife... you need to RUN RIGHT EFFING NOW, DUMMY!!!! RUN RUN!! GTFO!!!
This, of course, does not make sense when we're serving a second serve at Ad-out in a set deciding game... but our so-called "mammal brain" does not do a good job of telling the difference... it senses stress, and depending on the magnitude, begins cranking and shutting down our executive function and wrecking our fine motor skills (which we need more than our executive brain function to serve well)... To combat that, I use what psychologists call "grounding" techniques. The premise is that your brain cannot be in fight or flight mode, worrying about the saber toothed tiger AND SIMULTANEOUSLY be thinking "gee those pretty yellow and white moths flitting amongst the Queen Anne's lace over on the banks of the drainage pond sure are pretty on this fine summer morning". If you use your executive brain function to calm your mammal brain, you bring your fine motor skills back on line too...
These grounding techniques can take many forms and they are up to the individual... The bottom line on them is that they force your executive functioning brain to take control again and force the physical relaxation that will derail your "mammal brain's" panic that is trying to override your executive function. For me, I do a little deep breathing, physically imagine it banishing the stress and tension from my large muscle groups... I wiggle my toes in my shoes... take a look over at the drainage pond for a second and see if I can count the dragonflies or butterflies... look around me and silently name objects to myself "car", "baby stroller", "trash can", "lawn chair", "sliding board", "water cooler", etc. I let myself feel the sun on my shoulders, or the breeze on my face, or the dampness in the cool air, smell the charcoal grill from a block away, etc.
The above takes me between 5 and 10 seconds... then I step up to the line, feel myself get physically balanced, bounce the ball at least 3, if not 4 times perfectly back to my hand, and I try hard not to think things like "don't miss this one!", instead, I think "OK spin this one in, no big deal, catch the toss if it's sh*tty" and then... "OK here we go..." all of that takes maybe another 5 seconds...
Sometimes I still DF on that Ad-out serve though... but usually it's not because I was crapping my pants while I did it.
