I’ve actually agonised over that. The problem is that there is no polite and unpressured way to do it.
I wish there was some well known abbreviation for “look, you totally have the right to continue, and indeed if you have a plan please by all means do, but please don’t just keep playing out of politeness - if you don’t think you can win from here and it’s all the same to you how about resigning?”
Apart from anything else, you can be totally wrong:
GaJ