YSK: There is a breathing technique that some literature suggests activates your parasympathetic nervous system, which is tied to your instinct to sleep after eating. It can be used to reduce anxiety, trigger relaxation, and fall asleep at will. It's called 4-7-8.
from /r/YouShouldKnow
YSK: 呼吸法の中には、副交感神経を活性化させるというものがあります。不安を解消し、リラックスを促し、自分の意志で眠りにつくことができるのです。その名も「4-7-8」。