On bitterness

You know those people whose natural expression is just bitter? When they aren´t talking, listening or doing anything really, they just look like everything and everyone suck.

Bitterness is very noticeable due to the corners of the lips, that actually bend down, and the eyes that seem capable of burning.

I always hated the bitter face.

It just makes me mad.

But recently I´ve found that I´ve produced such face in more than one occasion. And that´s just plain scary.

How do I get rid of bitterness?