tiggz:
I always double check everything that way nothing can (hopefully) go wrong. I know alot of people that don’t apply the trailer break when dropping a trailer as they say it’s a pain in the arse. If it was a pain in the arse the trailer wouldn’t have the park break in the first place. it’s there use it.Good luck with the training too ■■
I agree, double check everything. I, as have almost all of us, forgotten to do the double-check, usually after being distracted by some thing. The forgotten double-check is usually followed by jumping in and pulling away. There then follows one, or several, differing disasters, depending on what has been forgotten and how far you get.
Some times the electric suzie pulls out and the stretched line whips the end against the back of your cab. Or not, in which case you will need a new set of airlines and electrics suzies. If you are really lucky you will remember in time and will only have to clean the grease off the stretched suzies 
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You might forget the legs in which case, if the trailer is empty all you have to do is put the leg winding gears in low and strain to wind them down against the weight of your trailer. If it is fully loaded 
Forgetting to pull the pin is simply embarrassing, as long as no-one else notices. Forgetting your number plate can be very annoying, you might have to pay for a replacement. You lost it, seems fair enough to me 
I know, I’ve done them all (though I didn’t actually drop the trailer onto its knees, I stopped in time).