Good question. A ruin IS an orgasm. Just often without the pleasure associated with it because you stop all stimulation as soon as you go over the ‘point of no return’. Remember, ruined orgasms are very intense, but also variable. They affect people in different ways.
So the two key signs you ruined are your arousal will drop (but with a ruin it’s often only for ten to twenty minutes’ AND your clit et al will get super sensitive for 20 seconds to 2 minutes (that’s the Post Orgasm Torture window for the sadists/masochists among you).
If you’re not getting either of those but you get a few throbs/clenches it’s basically your pussy saying, frankly, ‘Feed me dick’ to put it from an evolutionary biology perspective.
If you only get one of those, the first, where your arousal drops but only for a minute or two then that’s something that sometimes happens during a hard edge. More to men then women in my experience. I put it down to your body/brain basically saying ‘What the fuck are you doing, I’m going on strike’.
The big picture is really, don’t worry about it. If it feels good, you’re keeping horny and enjoying the denial high from whatever you’re doing then you don’t need to dig too deep into exactly if you’re ruining or whatever. As long as you’re not cumming, which is a deliberate, and almost always very obvious experience, then you’re being a good little denial slut and you should keep on at it!