I counted 4 of us 
Well Brothers and Sisters Paranoia rules the day, and why not, check and double check, and double check the double 
I allways take a glance at the pin when i return to the truck, aswell as walking around to make sure my lights havent been tampered with on the trailer.
One of my own little paranoias is taking the wrong trailer, I check the number on the paper work against the trailer number probably 3 or 4 times. One place i worked we had all the trailer numbers on the front offside corner, then you could read it in your mirror, as you pulled out the yard, all be it in reverse
Years ago i once pulled the pin on a trailer i was dropping before disconnecting the lines, or appling the trailer brake. And as you would expect it started to roll backwards off the unit, i quickly shoved my hand on the foot brake to stop it, so there i am stood by the unit hand on footbrake wondering what to do, eventualy i plucked up the courage to lift my hand, and as luck would have it the trailer wheels had settled into the dirt, and it stayed there as i quickly jumped on the catwalk to disconnect the red line. This little episode taught me to allways connect/disconnect in a certain order
But you never can be to careful 
One of my own little paranoias is taking the wrong trailer, I check the number on the paper work against the trailer number probably 3 or 4 times
Not just me paranoid about that as well then. 
Ive been very close to dropping a trailer,but i dont think it was my fault really, i was using a hired wagon for the day, a renault premium auto,and as any of you will know that have used one these heaps of ■■■■, they aint the best for getting controlled accelleration,so as i was nearing the pin i eased off and felt a CLUNK, thinking thats go it,lifted the suspension up abit,put it in drive to give a little tug and it all seemed honky dory so i finished coupling up,then as i started pulling off and turning out the yard i just caught the sight of my trailer sliding onto the run up ramps,i managed to catch it with about 6 inches to spares, i proper ■■■■ my kegs.
TBH we do play a little game where i work,and thats waiting for one of the freshly passed drivers to finish coupling up,then when they go to the bog or go the coffee machine before heading off,we pull there trailer brake on,then sit there in a little huddle waiting for our childish prank to get another victim,we normally give it 10 minutes of them walking round scratching there heads and checking there airlines before we go over and say “whats up drive” and get the reply “doh know,it just wont move” then we put them out there misery,well we have to cheer ourselves up somehow dont we
Another little story. At a place i used to work, the fitters unhitched the trailer off the back of this miserable old drivers 
unit,(wound the legs down right hard so as to take all the weight off the unit ), whilst he was in the transport office, then rang the office from the worshop to tell them to watch as well. This Bloke didnt notice that the trailer wasnt with him any more, until he went to back it into a spare slot amongst all the other trailers, 20 yards or so across the yard 
, needles to say joy was unconfined