I intended to send a mailing to only a small segment of a group. I wanted to make sure the message was only going to go to that group so I checked the email once more by heading to another page outside of "set-up delivery".  Once I knew everything was ready to go, I went back to set-up the delivery but I didn't check the groups because I assumed everything was ok....

Turns out it wasn't... 

I ended up mailing the segment I didn't want to email. I'm dealing with frustrated donors as we speak. Please have a save function for groups at delivery.