Behaviorally...

"Emotion is a chemical that can either be released through expression or stored through repression."  -Me

Expression and repression are choices we make, in other words, behaviors.  Repression is non-expression.  It is a refusal to express.  Expression takes the energy of emotion and releases it to the world.  Repression takes that same energy and pushes it down inside.

In the very short term, repression can be a helpful emotional tool.  If your boss comes to you and gives you an assignment that you don't like, bursting out in tears is probably not the best solution.  It's probably a pretty good idea, if you wish to remain in the job, to repress that emotion until you get to a place where you can express in private.  And if you do find a place to express in private, then repression is just a handy tool.  The problem comes when repression becomes the main or only tool that is used to handle emotions.

For many people, repression is by far their most commonly used emotional tool.  When their boss gives them that assignment they don't like, they don't go find a place to cry or yell.  They just swallow their sadness or anger.  They push it down inside.  The problem is that there is very real energy tied to emotion.  When they repress their emotions, they are also repressing that energy.  My belief is that the energy gets stored in different locations in our bodies and, in high concentration, is a significant cause of disease.  This is a problem.

The obvious solution is to express.  But most people have difficulty with expressing their emotions.  And expressing in public, for most people, is out of the question.  These difficulties come from a taboo in our culture against expression.  If we want to build healthy lives and a healthy culture, we need to break that taboo.

In my opinion, the best way to break the taboo against expressing our emotions, is to express regularly.  And so I do.  But I recognize that this presents a significant difficulty for most people.  My recommendation is to start connecting to your emotions, even if you can only do so in private.  Find a private place to sit or lay down and try to feel what you have inside.  If you do this regularly, you will forge a strong connection to your emotions and will eventually be able to express them any time you choose.  This is very good for you and for the world.  As Thich Nhat Hanh says, "Peace in oneself, peace in the world".