Hi Paul Lombardo,
Breathing is a movement, an expression of your body. Your body and it's capacity to breathe is basically giving you an opportunity to ride along - with the body as breath.
When it comes to self-expression, breathing is specific, in that it allows you to move AS the PHYSICAL EXPRESSION of the body. This gives you the advantage of being able to develop inner stability with and through breathing.
When you are breathing in awareness of your body, you will find that the mind as your thoughts has less of a hold on you. Therefore breathing is a key element in developing your self-expression. Breath is literally the BRIDGE between 'you' and THE PHYSICAL as the body.
You will thus find that self-expression and breathing are very narrowly interlinked, yet self-expression is not defined by breath only.
As you work with self-forgiveness in writing and in speaking it out loud, you will find that self-expression will come though in moments where you did not expect it. Self-expression will come though as part of an accumulation effect where you start to invest in yourself as life through breathing in every moment, writing, self-forgiveness, communicating, sharing.
Here is an interesting vlog from a Destonian made in 2008 where he speaks about the link between supporting oneself and developing self-expression: