I have no idea how you managed that. My sigmoidoscopy (they do not give you anything beforehand) was one of the most unpleasant experiences I've ever had.
The strange thing is that I also had a sigmoidoscopy 25 years earlier and it matched your experience of being very bad; I was about ready to confess if it would help. But the drug-free colonoscopy was pretty smooth. I think the second doctor was a much better "driver". But maybe endoscope technology also improved, smaller diameter perhaps? (One might also wonder why I went ahead with a drug-free colonoscopy after my sigmoidoscopy experience. I guess I don't learn from experience.)
I mean, it’s definitely unpleasant, but I have a hard time justifying any form of sedation for it. The sedation (especially full) seems more risky than the procedure in such case.