We had about 20 foals every year, and every year they had about 2 weeks of daily handling before mare and foal were turned back out with the other broodmares and foals. Daily handling included a baby lesson in leading out to the paddock, and back to the stall with mom.
No big deal, right? Not for the other 19 foals, anyway. Mind you, this mare was not our favorite. And she always seemed to have Less Than Clever foals. Foals who became Really Stupid Two Year Olds, I might add. Who then subsequently became No Account Three Year Olds Who Couldn’t Run Their Way Out of a Wet Paper Bag, Leading One To Wonder WHY Anyone Would Breed That Mare, but I digress…
Anyway, this particular little fellow had a problem with following mom with the aid of a halter and Ye Old Butt Rope (you really can’t call it “leading” - just getting acquainted with the tools of the trade while you take 75 steps following mom). Some more spirited foals get a little airborne and you just quietly contain them and mostly ignore them. Some just plant their tootsies, and you give them a a little bump with the butt rope, and then they notice mom is 3 steps farther than she was a minute ago, and off they go. It’s pretty smooth sailing for most foals in other words. Not real traumatic from their perspective.
Anyway, little L&L planted his tootsies about 10 feet out of the stall. Then little L&L felt the butt rope. Then little L&L started BAWLING like a calf - I have NEVER heard a foal/horse make a noise like that (I think it spooked his mom, but she wasn’t real maternal, so she started dragging her handler to the paddock). Then… all of a sudden he just started peeing!! We were totally flabbergasted! He scared the piss out of himself - literally! SO we bring mom back, make all sort of comforting noises, and manage to more or less get him to the paddock. Day 2. Repeat Above. Day 3. Repeat Above. Day 4. Repeat Above. About Day 5 he started getting the hang of it, but he was already named by that time. 
Needless to say he did NOT have the fortitude to become a race horse. Or much else, as far as I know.
“I have not failed. I’ve just found 10,000 ways that won’t work.”
Thomas Alva Edison (1847-1931)