I almost freaked a little while doing my advanced
PADI certification in Costa rica, it was a deep dive and I am not sure if it was a bit of narcosis but I suddenly really wanted to breathe through my nose and was wanting to be on the surface. I just forced myself to slow right down, half closed my eyes and focused on my breathing, almost trying to meditate a bit. hahah I actually flashed back in my mind to batman begins in the scene where they talk about mastering your fear. ended up finishing the dive like a boss and haven't felt it since. Im a big fan of identifying the fact its your brain trying to trick or controll you, ackowledging it and then realizing you have the ability to change your thought process.
another time I was worried was after some drift diving in barbados, it was the 2nd dive of the day and never having been sea sick in my life, I was starting to feel queasy from waiting for the boat on the surface during the 1st dive. before the second dive I had thrown up over the side of the boat and thought I would be good, but during the saftey stop at the end of the second dive I knew I was going to puke and was afraid of choking and sucking in water as a reflex. sure enough I couldnt keep it down and threw up through the reg, and forced my brain to slow down and think. remove the reg, continue to puke, clear the reg with the purge, put it back in, breath slowly, remove from mouth, puke again, and repeat the process haha. it was knarly and gross but I managed to keep my head and power through it. #gross