Oppression, anger, explosion

Did you ever shake a carbonated bottle of water, or soda pop or something similar? Of course, you have. The pressure inside the bottle builds-up. You can't see it but when you open the lid, the liquid explodes outward in a forceful spray. If you were to keep shaking it without opening the lid, eventually the pressure would be so high that the explosion would still happen. The bottle would break, spraying the liquid and pieces of the bottle in all directions, which is an extremely dangerous situation.

What does this have to do with psychology? It is an analogy for a person not expressing anger....