idk, i don't coach gymnastics, but i do coach football speed, track and olympic lifting. i have a lot of teenage athletes and also some adults (!) who at the beginning act a bit like this.
girls respond to being exhausted and/or not getting things as perfect as they would like them to be and/or being afraid to do something they are asked to do (often in olylifting when heavy loads are involved and you have to jump *under* them, then secure the bar overhead before it crashes down on you...) *and* want to do with being upset.
boys tend to get aggressive and/or just give up (more often than the girls in my experience).
these behaviours might not be very "mature" but they are perfectly normal.
hublaur, just try to trust your coach. he/she wants your best. try to keep calm, breath, count to ten slowly, refocus, get a drink or something, and then try again. if you can't make it happen today, do what you can do today (progressions!) and move on (to the shower or to the next station or...). don't get emotionally attached to movements/skills etc. observe, be rational, improve, and - *most important* - work hard.
when your body says "i can't go on", this is most of the time (i am not speaking of injuries!) just your mind trying to make you stop the work. don't listen to it. just refuse to give up and keep going till you are done. that's an important part of being an athlete. if your coach believes you can do this or that, you *are* capable of doing it. trust is important!