Well written, Mr. Wallace! Are you hiring? :)

Time is a slippery beast. You think you have it figured out, then stuff like this comes up. I guess that's why we're paid the big $? :)

Be Professional, Kind, and Thankful. Leave on good terms. Managers understand that people come and go; that's just life in business. You may find out the new job isn't so awesome until the honeymoon is over [6 months in]. Everyone is on their best behavior during an interview [including the interviewer], but people's real personalities come out 6 months to a year later. Maybe you'll find out your old job wasn't so bad after all? In that case, wouldn't it be great that you could contact your old manager about returning to your prior employer! Or, at the very least your old manager could give you some job lead contacts.