It's a minor social party for friends and it doesn't go very well. You've been there for an hour or two and it's not really lightening up. You want to go home but have no pragmatic reasons, you just don't enjoy the party anymore. But of course, it would be rude just to disappear, especially if there's only a few of you there.
Let's say you don't have any excuses or don't want to make up any, but you want to be sociable and say a proper goodbye when leaving to cut off the awkward feeling of both you and the host that you spent your time on something. You want to stay open but don't want to ruin your realtionship with your friends.
How to excuse yourself politely without making up excuses?