i always sigh cuz i need to take a deep breath and breath its almost like i'm subconsciously catching my breath or something idk maybe weird habit.
Usually because out of sadness, frustration, I find myself sighing sometimes when I'm tired but am in a situation where I can't go to sleep.
Most people sigh for 3 reasons...:P 1. they are bored... 2. they are tired... 3. they are h0rny...
It's a human emotion. Like smiling, laughing, just expresses someones emotions.
I believe it's a form of showing relief of stress.
To release stress and tension... (: :D
to show relief...