I've never sold a Bbag. My resources are limited, but I live in NY where it's fairly easy to do research on what I want, so usually by the time I get something, I am very very sure that it will suit my needs.
Sounds to me like the size is a real issue. I would sell it and get something else.
As far as seller's remorse goes, I would maybe take it out for a day and see whether the size really bugs you or whether you get used to it. Then you can be REALLY sure.
And the timing, I would wait a little bit, unless you're pressed for money. Now is a slow time when everyone is buying for others, and after the holidays most people will be broke. Also, the longer you wait, the more value the color will have - as tends to happen with bags that haven't been around for a while.