Forced smiling is a simple and easy technique to give yourself a quick mood-boost! Forcing yourself to smile can trick your brain into believing you are actually happy and release the corresponding neurotransmitters .
Just smile for 2-3 minutes.
Momentarily increases feelings of pleasure.
Improves emotional response to stress 
As long as you can hold the smile.
Forced smiling involves a process called facial feedback. By producing the facial expression of a particular emotion on your face, your brain gets tricked into believing that you are actually experiencing this emotion . A cascade of neurophysiological processes corresponding to that emotion are set in motion.
Whenever you feel you want to boost your mood.