I've sat on the rail of a bridge for quite some time, but couldn't bring myself to jump.
At first, I googled the highest bridges in my country. One was in my state and a railway bridge, over 100m (350ft) high and while it was partially above a river, the river was very narrow so there was enough space at the highest point to land on concrete.
It was still ~3 hours away from me by train, so I did quite some research beforehand, googled the bridge + suicide, checked the police's facebook page, etc. That way I found out there have been a couple successful suicides and no measures against it. The best thing I came across was on some obscure forum were actual instructions on how to get one the bridge, that there weren't any trains between 2am and 5am and how the police can't check it, because it belongs to the railway system.
Which means, high enough and not very risky to get caught.
I took 3 trains to go there, my last one arrived at ~11pm, but i decided to ride one station more because i didnt want to cause any suspicion and had a couple hours left anyways. From that station, it was a 40 minute walk trough the woods to the bottom of the bridge and it was really impressive. I layed down on a bench, ate something and watched some trains pass by. Then, at 2am I slowly got ready, walked another 10 minutes through the woods and was practically right next to the rails. I could see some houses and the train station, all i needed to do was climb over a fence that was at hip height and i was on the tracks. From there, it was just a 50m walk to the start of the bridge and another 200m walk to the middle.
The entire time i was scared shitless of someone seeing me from far away and calling the police. When i sat there, everything was calm again and i felt like nothing mattered anymore. I have absolutely no fear of heights, but even after closing my eyes i couldnt get myself to jump. I dont know how long i actually sat there, i just remember getting up after a while, thinking "wtf am i doing" and running back.
There was no train home at that time (4am?), so i wandered through the woods and part of a city for some time and took one home from another station a couple hours later.
Looking back, everything just feels really surreal. I can still recall the details and everything, but it genuinely feels like it was another person doing that and not me. The note i wrote and left in my room is still were they were supposed to find it, the bag i took with me there isnt unpacked yet and it has been months.