Most people sigh when they are unhappy or even when they are happy or feeling content. So the big question is why do people sigh? A lot of people want to find out why. So here is why people sigh.
Sighing is the opposite of yawning: it is an output of air, rather than an intake. Like yawning, it is something inexplicable, happening partly as a reflex, and partly as a means of expression.
Sighing is only significant when it happens to a person who has lost blood. Deep sighing respiration can show that a severe anaemia is present.