Helium exit bag

I have tried 3 times to use the helium exit bag. The first time I started to hyperventilate and chickened out. Second time I had a leak and had air in the bag. Third time I hyperventilated yet again. So what am I doing wrong? All the instructions say that the body is tricked by using the helium and yet I am hyperventilating like crazy. The other thing is that the instructions say that unconsciousness is found to happen in a mere 5 seconds or so and just a few gulps of helium will do it – that’s simply not the case. So what is it that I am doing wrong?