Concerns about how stress may result in not performing properly when you're alone ... then not performing properly when others are watching .... then not performing properly when competing against others ... are all well and good. Happens to all of us.
However ...
You might do some reading about the hormonal fear response and the physiological changes that occur in the human body. It can differ somewhat from the simple physical stress response to doing some jumping jacks, pushups and running 50 yds before shooting at some well-controlled range, in an environment where someone isn't shooting at you.
Consider reading some of the work by Lt Col Dave Grossman.
http://www.killology.com/art_psych_combat.htm
http://www.killology.com/bio.htm
Working to systematically and repetitively ingrain
proper skills and skillset reactions is usually a good idea, as then you have a better chance of them being accessible under duress. This is one of those difficult processes, though, since failing to do correct training & repetitions can potentially be one of those "2 steps forward and 3 steps backward" kind of things.
I can't remember where I read it, but some years ago I came across some study involving college athletes (as if
that narrows down the literature
).
One of the surprising things observed was that even after
proper repetition & training to perform some newly learned physical actions had occurred, it was observed that it was still possible that doing an
incorrect repetition once might require a subsequent 10 additional correct repetitions to restore proper performance potential that had been acquired up to that point.
Maybe so. I've certainly had days like that, myself.
Part of the potential answer might be to seek out some reputable trainer & training, done in a supervised, controlled and safe manner.
Normal human reactions when confronted by an unexpected set of circumstances which may present a danger seem to run along the lines of
Freeze, Flight or Fight. It's been hard-wired into us for some time (although I look at it as more of a
software thing).
Proper training ... AND Mindset ... can help to mitigate the effects of such startle and stress responses in folks. What's also been called trying to
inoculate ourselves against the unwanted, but predictable, effects of how we react to things.
In other words, being able to subconsciously access an ingrained response, or set of responses, when our conscious thinking is compromised by bad things happening.
Science has been studying this sort of thing for many years, and some interesting answers have been developed.
Good
initial training, followed up by some
recurrent training, maintained by
proper practice (which often seems to work best when an impartial set of eyes are watching) doesn't seem unreasonable to help many folks achieve their goals of becoming better able to react, act and respond under severe stress.
How many people do you know who have developed good defensive tactics or martial arts skills by being self-taught, though?
Even once properly learned, or even mastered, physical skills can be perishable, you know.
Just some thoughts.
I've been a LE firearms instructor since '90, and I've been involved in the pursuit of various martial arts since '71 ... and I still don't claim to have any particularly definitive answers to these sorts of questions.
Usually, whenever someone has cause to see me perform something difficult or advanced, in either the arts or with firearms, and they express some admiration or desire to reach that level themselves, I inwardly shake my head and accept that they don't have the ability or experience to actually recognize how poor I consider my "performance" to really be, or to recognize my shortcomings.