From How I Met Your Mother:

The steps normal people go through before saying "I love you".

The moment when you think you think it.

The moment you think you know it

The moment you know you know it, but can't yet say it

And finally, the moment you know you know it, and can't keep it in you any longer

http://www.youtube.com/watch?v=NTWmMCliPsU&feature=related

Sweet Memories
by Seiko Matsuda, Olivia Ong

なつかしい
痛みだわ
ずっと前に
忘れていた
でもあなたを見たとき
時間だけ
後もどりしたの
幸福？と聞かない
で うそをつくのは上手じゃない
友だちならいるけど
あんなには燃えあがれなくて
失った夢だけが　
美しく見えるのは何故かしら
過ぎ去った
優しさも今は
甘い記憶
sweet memories

Don't kiss me baby
we can never be
So don't add more pain
Please don't hurt me again
I have spent so many nights
Thinking of you longing for your touch
I have once loved you so much

あの頃は
若過ぎて いたずらに
傷つけあった二人
色褪せた
哀しみも今は
遠い記憶
sweet memories

The song that is stuck in my head now. I guess it fits the type of song i like, the piano solo, the haunting voice and most of all it was released in 1983 by an old renowned singer.