I've noticed a lot of people do certain things while gaming in order to win or do something important. What do I mean by this? People move with the controller, repeatedly press "A" or "X", hold their breath, etc. even if it won't/can't change the outcome of the game 

Do you do anything like that to win? Or have you seen other people do things like the mentioned?

I know for instance in Pokemon when I throw a Pokeball I press the "A" button repeatedly... even if it doesnt actually help XD

My computer chair turns so as my Kart turns in MK8, I turn my chair but not my head... You can say it doesn't help but fuck off, if I believe it helps, it helps

I continuously shoot in Metroid games, because I keep feeling like there's a hidden detail that I'm gonna miss T-T

When I was younger I used too turn the actual controller in the same direction as I was steering, when I was playing racing games.

In Pokemon I used to tap the B button, thinking it helped keep the pokemon in the ball.

It depends on the game.

For instance, in Fire Emblem games, I keep resetting to avoid that one little fatal hit...

Always do this too, just a perfect rhythm of shooting until something sticks its head up and then go crazy or charge up and let rip on it. In Metroid Prime they added that lovely ripple effect to the shots and lighting as they travelled accross the environments too which gave a little treat to doing this, such a beautiful game was a shame it launched alongside Halo, really overshadowed the first Metroid Prime.

As for other bad habits in games, if playing a close match in Street Fighter once it gets down to the last 1/3 of health bars I find myself pretty much holding my breath focus'ing 100% on just the game until the round ends with a rather large gasp.

I constantly shoot in overhead shooters, even when there are no enemies on screen.

i just play to win

What i do to win a game?
Pay a lot of money. I love pay to win games!
No seriously though, the same for pokemon!

Also sometimes holding my breath, but that rarely helps.