Every now and then I just jam over backing tracks. I guess it is kinda like Schmange said, I try to learn something new, try try try then I get frustrated so I put on some backing tracks for a few days or record endless riffs and stuff, then come back and often I find it easier ... I never actually thought of it has being subconscious but it makes sense.

When I jam I usually don't think about anything, I just try to play in different places on the neck .. sounds weird right? but that's what I do. It forces me to break out of my usual comfortable spots I know too well.