Maybe I should be more clear . . . Let's assume you knew both the direction and magnitude of the stocks future move, but you didn't know the path. In that case, you might try to increase your gains by holding out for a better price. Of course, you might miss out on some of the move if you don't get a better price . . . but that's the risk you take. In that scenario, you're trying to improve the price. So buying lower makes sense.
But in the real market, you don't know either the magnitude, direction, or path. So you have to choose the set-ups with the best expectancy. Those are the strong stocks. By buying lower, you're ignoring expectancy to improve price. That's the lump of gains fallacy -- but gains aren't predetermined, they're uncertain. And you're already imagining that the move is predetermined -- the fallacy of the predetermined move.