You don't get near death experiences just by holding breath, not even close. You might eventually be able to make yourself pass out though, so never ever practice long breath hold under circumstances where a loss of consciousness would be a danger, e.g., while driving, close or in water, close to streets or high drops or stairs, etc.

Lethargic states stop you from doing what you want to do and to manage your time effectively. Allocate time being in such states for resting or sleeping hours.