Consider this fictional situation which I made up to let you feel the sense:
Brad and Brett was chatting about recent thefts where cheats were making hoax and decieved the victims. While Brett was talking about a particular case of this kind of theft, Brad remembered he himself was duped in a similar way and almost went to tell Brett but swallowed his word thinking Brett might use this fact against him later in future to mock him.
So what is the word for the italicized phrase? I thought about "choke". But something tells me it isn't.