First, it's the conversation between Ted and Jeannete when Ted was trying to get Robin's locket back:
T: I'm being crazy?
J: Yes! How long have you been hung up on Robin? Eight years?! And you're still killing yourself to fetch dumb little trinkets for her. That's crazy! I don't think there's a word for what that is.
T: Actually, there's a word for that. It's love. I'm in love with her, okay? If you're looking for the word that means caring about someone beyond all rationality and wanting them to have everything they want, no matter how much it destroys you. It's love! And when you love someone, you don't stop, ever. Even when people roll their eyes or call you crazy, even then, especially then! You just, you don't give up. Because if i could give up, if i could just, you know, take the whole world's advice, and move on and find someone else, that wouldn't be love. That would be some other disposable thing that is not worth fighting for.Second, the beach scene when Robin insisted Ted to tell her the reason why he wouldn't ask her to not being friends anymore to save his relationship with Victoria:
R: I would have understood, you know? I mean if you told me that we couldn't be friends anymore, i wouldn't have liked it, but i, God, i would have understood
T: I could never do that
R: Why not? Ted, okay, i insist that you tell me why not
T: No way
R: Answer the question, it's for the bride
T: I'm not gonna answer the question because you know the answer. You want to talk about my top five? There's no top five, Robin! There's just a top one and it's you. And the only reason i'm saying any of this is cause i know that it's not gonna change anything, you and Barney are getting married today. If i have to hold the shotgun myself, it's happening
And at the end of the scene, Robin flew away and Ted finally let her go. It's very relieving and saddening at the same time. You know, it's been eight years he has not move on and now she finally has to go. That marriage really is the finish line for him to wake up from his delusion that he would someday end up with Robin.
I know you can't easily move on. Maybe we said we already move on but there's always that tiny hope in your heart that you somehow gonna end up with him/her. Until you finally see the finish line clearly like Ted, it will always be blurry, you'll never really move on.