How do I cancel a game?

I only wanted to play with a specific person but somehow I've ended up with two games going. How do I cancel them? 

Thanks - rev

if you have not moved yet, next to offer draw/resign choices is "Abort," but it is only there if you haven't moved yet.

So if you have moved, you just have to let the game expire?

as far as I know. I accidentally started an online game, and had to play it out. So I'm probably not an expert on how to cancel it.

Are you worried that your rating will go down ? If you have only moved 1 or 2 times and then no more the game will end on time but you will not lose any points. I think? But that would be rude to your opponent. Just try and hit the abort button I guess.

Being rude to the opponent and wasting his time was really my concern, not my rating. Resigning as a way out is not much better. I think the best way would be to leave an explanation in a Chat comment - that offers me a way to apologize to an opponent for inadvertently starting a game.