I had a friend who solved the structure of 2 or 3 new proteins pretty much by himself his senior year of college. I also had an acquaintance who was a PhD student in the same lab, who said (jokingly) that she hated him because she had spent 5 years on a single protein and got way worse results than he did. I got the sense from talking to them that the process of figuring out how to get a protein to crystallize is basically just trial and error over and over—my friend himself said he basically got very lucky several times in a row (though he is also a brilliant biochemist).

Anyway that anecdote is pretty much the entire sum of my protein crystallography knowledge, but perhaps it explains how your experience and GP's statement can both be true?