'SI' as I understand it is "self injury".
When I am 'pushed into it' by my self-loathing and almost hysteria, it is a way to try and get control over my overwhelming emotional pain and the tears that will NOT stop when I want, or need them to. Sometimes the emotional pain is so deep and 'scattered'; about the past, the present way I am 'failing', and fear of the future, that a hard slap to my face can 'force me out of the tears' sometimes. I am embarrassed to admit that I do that, but it is the truth.
Thankfully, my episodes are few and far between these days, but the emotions of losing my dad, and the flashbacks of being there when they were performing CPR are too vivid. When the doctor told me they had not had an oxygen level for 20 minutes, I told them to stop. Although I know it was the right thing to do, and I am glad I was there for his last moments, it causes more pain than I can hold in. I try, for his sake, not to self-injure, but sometimes I have no control.
My first episodes of that type of self-injury occurred after I held my daughter in my arms as she died 20 years ago this year. Sometimes it seems like just yesterday. I 'go back' to what I think I could have, should have, done differently. The same as I feel about my dad's passing. I know from past experience that these feelings will not get easy by any definition, but easier as time goes by.
In the past, I would do it until my face was beet red. I've never left obvious bruises which I would have had to explain. I have been able to hold it to one or two hits in the most recent episodes. I know it is NOT a 'tool' for self-control, and fight my best to keep it out of my head.
I also dig at my head until holes appear and can last for months. (this is hard to admit) I have been able to 'curb' that by having acrylic nails which are not as sharp as my own nails. It is expensive, but I figure it is better than ending up with permanent patches of hair loss, or getting a staph infection.
My T is aware, and I always admit to him that I've had a repeat episode. I then agree to try and not follow through with the 'desire', and write down the feelings I am having so that we can discuss them at the next visit. It doesn't always work.
I will never give up on the healing I desire for this behavior, and be able to say it is permanently in the past.