Asking Jesus into your heart is a dead horse of a phrase that's been beaten by, I don't know how many clichés.
It's one of the dearest and perhaps most important ideas to have cemented itself into the vocabulary of evangelical Christianese.
It's also a really powerful thing to do.
To be lost in the dark and not to lose yourself; to be sucked down, and call out to all that is; to ask Jesus how the hell he did it, and then to become him, until your hell is his hell, his power is your power, his resurrection yours. Where does the vine end and the branch begin? The sap flows freely through.