I don't remember using my imagination when I was a kid feeling like something akin to jumping off a cliff. I'm still finding it a challenge to rely on what I see in my head instead of something right in front of me, but it seems to be getting easier. If I have to suffer through sweaty palms and heart palpitations to get a drawing done, so be it.
I'll just tell myself it's excitement.
Still, with my fear of heights I think these thrills will be as close as I'll get to the ones skydiving enthusiasts rave about. That's perfectly fine with me.