My anecdotal experience of such events is two fold... One time I actually considered doing this but when it came to it I realised that, no matter how hopeless my situation seemed at the time, I am an optimist at heart and jumping off a bridge isn't something I'm ever going to actually do.

Secondly, same bridge a few years later, I encountered someone contemplating a jump and tried to talk him out of it. Relating the above and pointing out that life had turned OK after all didn't do much to dissuade him. Convincing people not to do it is not as easy as one may imagine. I soon figured that everything I said was just making matters worse.

Anyway, thankfully, I manged to flag down a passing ambulance and they were able to handle the situation much more calmly, he didn't jump.

One of the paramedics told me not to be hard on myself for not coping so well, she said the ones who are going to jump just do it. The less committed are playing the idea through, like I was, and are hoping for some kind of intervention to help them out of their current mindset.