Used to work on roof tops and everybody got the feeling and it bothered everybody a little but you just got used to it.
For me, it was a thought like "I could totally just walk over the edge... Whoa that would be so stupid, why did that even come to mind?".
I see Alastor's point about the "urge" part being calculated or cerebral. It is as if you just notice a fact, that happens to be true, that it is possible to jump, and then the reaction is strongly emotional: "no way! what did it mean that I just thought that ?!"
Always reminded me of something from back in sunday school. Matthew 4:5