My question is, can you remember a time when you reached your threshold of loss while gambling?
A true gambler doesn't have a threshold loss, one would only stop if there is nothing else you can sell to gamble with.
I don't understand, what do you mean sell? Obviously, you need money to gamble, if you don't have so it's better to stop. Maybe what you are referring are those addicted ones, that there are really dependent and willing to sell anything (as you have described it).
For me the threshold is that if I don't have any money to play, simple as that. I would not go to length to pawn or sell anything. I have my priorities now and gambling is not one of them. I just have to scratch that "itchiness" from time to time, that's it.