Exactly.

How exactly do people think that so-called Indian Yogis can accomplish feats such as levitation? Or how Buddhist monks and Qi-Gong masters have spent years emptying their minds (transcendental meditation) and denying their bodies in order to reach "nirvana" and perform things that are not natural to normal mortals? Because they are taught to build their "chi", which only grows stronger by hoarding spirits (demons) into one's being.

Anyone who opens themselves up to this practise isn't just messing with their spirit. They are opening a portal and inviting spirits into their being.
It's the same as messing with a ouija board. People just don't anticipate that there are malevolent spirits behind the veil.

Be careful. It may be easy for you to get into this, but it's a nightmare getting back out and in the long run astral projection, channelling and all these practises enslave you. You can't live without them and they begin to take over your life. When you finally realise and want out, you're plagued by demons. Some people even develop multiple personalities and become depressed and suicidal. It's not worth it, trust me!