I believe, without a doubt, that I would significantly increase my investment in poker; devoting more time, money, and effort to studying the game, among other things.
I wouldn't consider quitting unless I perceived it as mere "luck" or if the prize didn't accurately reflect my skill. But personally, I find it highly doubtful, if not impossible, to reach such a winning figure solely through luck or chance.
And, in the scenario where the money comes from a source unrelated to poker, I wouldn't cease playing but would adopt a more relaxed approach.