How high is the bridge you're jumping from? Also are you landing on water or land? I know you may have already considered these things but the fact that you said, "Guaranteed death" has me concerned. Death is rarely guaranteed from jumping. Looking back at an old suicide website I used to look at when I was planning on jumping, lostallhope.com says you need to be 150 feet above land or 250 feet above water to have a death rate of between 95-98%. If you're jumping over water some of those deaths included in the statistics are from people getting injured then drowning. Landing on a car could cushion your fall.
You sound like you could access sn, so unless you have access to a bridge that's significantly higher than 150 feet over land, I would strongly recommend using that method for your own physical wellbeing in spite of your fear.