In all seriousness, I'll think of a little idea to try out in the solo and go from there. This may be a melodic or rhythmic motif that I'll start with. The rest of the solo I'll think about the underlying changes and the rest just kind of happens on autopilot.
That's one reason soloists should keep a 'tool box' of patterns and musical language handy. As Smooth_bass said, it's much like a conversation - you'll think about what you want to say before you do, but as soon as you start the conversation overthinking every word you say may be detrimental to a fluid statement. Of course there are situations where you may want to put each of your words on the scale, like in court, but usually you're not in court when you're on stage taking a solo. The analogy doesn't quite take us that far.