Internal Family Systems Therapy has been a lifechanging method of self therapy for my partner. He doesn't have full DID but he is on that dissociative spectrum and he always though of his psyche as being composed of "aspects" with different desires, personalities, ways of reacting to things etc. When I found out about IFS and sent him the books it was a revelation and has done more for his mental health than any other form of treatment he's ever had.