I used to dissociate constantly in and out of my therapy sessions. It was how I coped during my abuse and I would default to dissociation as my coping mechanism when I felt distressed or unsafe. Over time, I learned to actually recognize when it was happening while it was happening and learned how to keep myself present. It took understanding, believing, and trusting that nothing was happening to me in the present that would harm me. It also took getting to the point where my history truly became history for me and stopped having constant power over my present-day life. So obviously it was a slow process, but I did get there in time. I almost never dissociate now, and when I do, I don't go nearly as deep, the duration is much shorter, and the after-effects have much less impact.