Full suspension was actually my first sui attempt. It was quite uncomfortable as I used a thick fake leather belt so it was tricky to get the positioning right. Had no proper knowledge so I just did what felt right.
SI kicked in once my vision started going black around the edges. I used a curtain pole and stood on the edge of my mattress which made it possible (albeit tricky) to back out. Took a bit to get unstuck and SI was too powerful to try again.
For me personally, I wish I fought harder with SI that day since the anchor and ligature held really well. Oh well, I am appreciative of some things I've experienced since.