Board Thread:Spoilers/@comment-25095167-20140623052851/@comment-25132702-20140729164910

Grayman44 wrote: Why do you guys think future Rigby had to come back and say this? What bad thing do you guys think caused it?

That's true. Assuming that Rigby screwed up, then we'll see future Rigby again. Possibly Rigby giving the message to his past self.
 * EDIT   Ok so I watched it again and found some things out, future Rigby says he needs to stop the kiss because it will be the only way Mordecai will be happy, also Skips mentioned Rigby will probably fail because the wheels of fate were already in motion, and finally future Rigby said that the only way he'll see Rigby again is if he screws up, so now we have a bit more info.