Marshall: Barney, I really don't think this is gonna help.
Barney: Do you know why you're not over Lily yet? It's 'cause you can still picture her naked. You can't get over a woman until you can no longer picture her boobs. It's a scientific fact. The average male brain can only store a finite number of boob images, or BPEGs and your hard drive's filled to capacity with Lily's.
Marshall: There are a lot of them.
Barney: They won't go away until you overwrite them with images of other women's boobs. Now, this journey may take as many as a million boobs so we begin here tonight my friend. Two at the time. Those count as four.