Why do i feel like crying sometimes when i am extremely tired and/or under a lot of stress? does crying relieve stress? if so, how?

Expressive outlet: There is a neuronal connection between tear duct & emotional brain regions. Chemicals are released during emotions & tears serve one outlet. Socially they communicate; psychologically they may soothe or produce aversive sensation prompting action to cope. There are numerous theories which reflect the complexity. Most women feel better after a good cry, if it relieves your stress, enjoy the effect.