How many times is it now that Sam has done his narna, and broken-up with Dean?
His What?
Now Sam has left Dean for several reasons, some times meant for brief periods other times meant for longer.
Season one, he left Dean because Dean wouldn't listen to him and instead followed orders from their absent father. He decides to came back, and manages to arrive just in time to save Dean's life.
Season two, he takes off from Dean to figure out why John thinks Dean might have to kill Sam. Basically to try and figure out what happened to him. Dean tells him to wait (this after Dean lying to him for months). Sam does manage to discover some hints. Dean is the one to follow him and decides to stick with him.
Season Two Sam is possessed by "Meg" and takes off, it takes Dean about a week to find him (still possessed).
Season two, YED transports Sam away from Dean.
Season three Sam briefly leaves Dean to research an immortal in hopes of saving Dean from his deal, Dean domes after him and in this case saves him.
Season 4, Castiel frees Sam when he is suffering the worse withdrawals from demon blood (enough so that is his physically getting thrown around the room, and seeing visions of people).
Season 5, Sam realizes that he can't trust himself (and that Dean doesn't trust him) decides to give up hunting. Dean thinks its a great idea. Sam wants to come back when he discovers that whether he likes it or not, Lucifer wants to use him as his meat suit.
Season 7 Sam leaves Dean (who has a broken leg, to go on hunt).
Season 7 Sam leaves Dean because Dean has been lying to him , killed his friend, and doesn't trust Sam. Decides to work with him again, when Dean actually talks to him, instead of lying to him (ie explains why he did what he did).