ditto that skatesailor. also, judgment sometimes comes down to trusting instinct. even when you are dealing with something new, instinct will often tell you what is right and what is wrong.
had a colt born once where everything went wrong from the start. colt got stuck, mare wouldn't let it nurse, thing developed pneumonia, and it turned out the colt had a hole in it's palate so that it was continually aspirating milk into it's lungs. after two months of nursing this colt along, i figured he was not meant to be. as a last ditch thought, i pulled him off his mom. turned out that when he was not tipping his head up to eat, he didn't get fluids in his lungs. on hay and mash, he did fine. he's 12 now and still blows food out his nose, but he hasn't had a sick day since. :-)
there was nothing wrong with the vets advice. there was nothing wrong with the treatments the vet advised. thing was, i was the one watching him every day. i had to make the decision even though it was not one she agreed with at time.