Talking to my kid, a bit of it seems to be - maybe not really “luck”, but the serendipity of meeting up with the right person at the right time. Kinda like dating. He pursued agent after agent, with no success, and then somehow hooked up with someone who saw promise in his writing. Then they sent it off to publishers with no real success, until it crossed the desk of an editor who apparently is a military historian and perceived the Congress of Vienna connection.
But it kinda makes me think, if s much depends on serendipity, why shouldn’t the “good luck” continue? 
Of course, as my dad used to say, “The harder I work, the luckier I get.”