lucky enough to cast a non-working spell? if you mean casting a spell that wasn't written properly [wrong ingredients, or a poorly written chant] you could in theory be able to add enough energy and focus to make it work in your favour. you might also wish to rewrite it slightly [be careful with the chants though, saying 'burn away what stands in my way' sounds cool, you wouldn't want that to happen literally]
if you mean 'turn me into a dragon' would work with a little luck, no. magick still works within the laws of nature, and even with luck, no human can physically transform into anything else by nature. you might wish to look into astral projection, but as far as the physical is concerned, no amount of belief, energy, or luck will make fantasy spells reality.