Once I catastrophically failed at croissants; next time, same recipe, great success. I have chocolate chip cookie recipes whose success is entirely dependent on butter temperature. It's incredibly important and harder to gauge. Yeast is easy.
I have the utmost respect for pastry chefs given how much more exacting their work has to be than any other kind of chef. They definitely get the short end of the food-respect stick. I've forgone choc chip cookie heartache by just melting the butter and using it that way. That might sound like sacrilege but it comes straight from Cooks Illustrated and those guys have a kitchen lab and wear bow ties even when it's not prom 1989 so, you know, they're pretty serious. Is the croissant success reproduceable now? Or is it like leave it up to the gods to decide whether my breakfast makes me sad?