There’s an apocryphal story about how my Dad and Peter Milner discovered the phenomenon of reinforcing self-stimulation (“the pleasure center”)–the stimulating electrode was in fact bent and went into the medial forebrain bundle quite by accident. That was the luck. The scientific success came from recognizing the resultant behavior and following up on the histological data to see where the stimulating electrode actually went.
As far as I know, the above story is true.
But the combination of luck and good science are behind many significant discoveries. The key is to work hard enough to generate your own luck and then to be imaginative to recognize a lucky success for what it is with subsequent follow up experiments.
That’s the best advice I can give for a young experimentalist these days.
Discoverers and Discoveries 