I'm going to date someone else after promising to come back to a girl
Do you have a good reason for breaking it off again?
I had my doubts after all, she is a sweetheart after all.
That's nice you decided on which girl to have, but you still made a promise to the former one. It's rude and unchivalrous to break a promise when it comes to dating. If you were able to betray her that easily, what says that you won't do the same thing to the new girl?
Shitbucket. Fine, I'll have to send a message and apologize.
It is good to keep your promises. If you can't it is better to tell people and give them an explanation why you cannot keep the commitment.