Knocking oneself out?

OK, I will show you how to knock yourself out painlessly but make very sure that there is a person stand by and something soft to fall on. You can start by lying on a bed then put a plastic bag over your head then start inhaling and exhaling within that plastic bag with one of your arm held up in the air. As soon as you p out, your arm will fall down and your friend that stand by can immediately remove the plastic bag to save you. Have fun.