I think I won that bet so I'm not going to give them the item I wagered.
Why won't you give the item to them? What makes you think you won the bet?
They say otherwise but I have my reasons. I know I won and that's all that matters.
If you lose a bet, you should pay up. You should make sure you lost, though.
But I'm telling you. I think I won.
It's nice that you're so confident but you can't just declare you won when you didn't. At the very least you need to discuss with the people you were betting with to plead your case as to why you won rather than being selfish.