The technical definition is holding onto yourself in the presence of someone else.
A big part of "holding onto yourself" is simply keeping your cool. After years of marriage, spouses become masters at pushing each others' buttons. I may interpret an innocent-sounding comment from my W as a dig or a criticism. How I respond, is, of course, totally up to me. I could escalate and let my angry side take over, accusing her of this, that and the other. I could let the comment go or perhaps turn it in a direction I want to go. This requires keeping your cool, not falling into the trap of previously learned behaviors. Not letting your spouse dictate your feelings and actions.
Easier said than done, right? I personally feel that a key to holding onto yourself is taking care of yourself on many levels. If you are easily agitated when you drink, don't drink. If you argue more when tired, get a bit more sleep. The key is making yourself better so you can weather the storms that surely will come. Posting on this board and reading posts has helped me prepare for the difficulties that lie ahead. Reading has helped, too.
A differentiation song:
You, when you're on the road must have a code that you can live by.
