Another Fine Mess

Yes, I have gotten myself into another fine mess. (I really have too much going on)
I have been wanting to see a sumo match for years. Since I live in Japan, I thought that I should take advantage of this. One of my co-workers is a sumo fan and promised to plan a time when some of us could go with him. I was very excited when he sent us a text message that tickets were on sale. I dropped off money for him, told my friends, and then last night, it hit me.
I had forgotten that I had agreed to go with the English Speaking Society on their spring retreat. As their guest, they have already made arrangements for me and paid my way. As much as I want to see sumo with my friends, I am already obligated to go to this retreat. I am hoping that my co-worker will be sympathetic and invite me along the next time. I feel really bad, because he went out of his way to include us in his plans and now I've messed it up.
I haven't talked to him yet, but I probably will this afternoon. I'm just hoping that I got the dates wrong and that I can do both. Guess will find out soon.