I've had a commitment that's lasted about 3 weeks, but I want to abandon it now.
Why would you want to do that, what else do you prefer to do tonight?
I would like to watch a friend play pool.
When you make plans with someone in advance, you should honor those plans unless there is a pressing need to cancel. It's considered rude and inappropriate to walk out on a 3 week commitment since it is going to result in someone having to scramble and find a replacement for you. If you are walking out so that you can do things like watch a friend play pool, that is not a valid excuse and you should instead go and complete what you first agreed to do.
My friends are more important than reneging on my responsibilities.
Friends do play a big part in your social life. But if you make a commitment you should stick with it.