Jim, I have experienced the same thing from time to time. Sometimes the problem is that BIAB has very specific sounds and if they do not fit your vision for your song it can feel forced, kinda like someone else is writing your song. Nothing wrong with the advice to go with it and let BIAB determine the feel of your song but also nothing wrong with dropping back to your own instruments until you get the song at least roughly fleshed out just like you want it.