The above quote is said by Jacob to Jack in the S5 finale. I've been puzzling with it, trying to reach an answer as to what Jacob meant. I would like to hear your thoughts on my ideas and suggest your own if you have any, here goes:
1) It could mean Jack needs that little "push" or realisation that he is special? 2) Jack should believe in himself more, have more faith perhaps? 3) Could be a reference to an event (plane crash and what came with it) which will change him into what he is destined to be (leader of the Island?)
The last suggestion there is the one I've strayed towards, as I feel as if he has doubted the whole destiny/mythology malarky but in S5 after his meeting with Locke at the hospital he was clearly affected and then Locke's suicide note made him believe. Jack's conversations with the likes of Ben and Richard kind of suggest Jack is more important than Locke is to the Island. Anyway, enough from me, discuss!