That seems to be the question my writing partner and I keep coming around to. Though we've both been writing our whole lives, publishing is a pretty new fanged monster to us. Neither one of us was particularly gutsy in trying to get a whole story out there to the public, despite the fact that we've both been involved in numerous writing groups and have tons of fantastic friends who also enjoy writing and reading. (Fun factoid: I met my husband in a writing group, maybe one of the first writing forums like it ever, thanks to then Tor Books!!)
What did we do to finally leap off the cliff? We held hands.