My MH nurse who visits me at home says that SI has been such a part of my life for so many years as a coping mechanism that it is natural to revert back to it when the urge comes up. Lessening it and even stopping for periods are great but the 1st instinct will be to go what I know best and what has worked for me over the years. When I do slip up my t and I just go back to our CBT work and focus part of each session on that to try and reduce/stop the SI again. She also says that the addiction is just like somking, and for many smokers when they quit the urge/craving never goes away; instead they have to fight it every day...
It sounds like you have a lot of resources, skills and strength to help you in this journey so I wish you luck.