This dialogue is the opening of the song "Aankhen khuli ho ya ho band" and it is spoken by Shah Rukh as he remembers Megha before blowing the candle on his birthday cake.
Ek ladki thi deewani si
There used to be a silly girl
Ek ladke pe woh marti thi
She admired a boy
Nazrein jhukake, sharma ke
Eyes down, shyly
Galiyon se guzarti thi
She passed through the streets
Chori chori chupke chupke
Slyly...quietly..
Chitthiyaan likha karti thi
She used to write letters
Kuch kehna tha shayad usko
Maybe she had something to say
Jaane kisse darti thi
No idea who she was scared of
Jab bhi milti thi mujhse
Whenever she met me
Mujhse poocha karti thi
She would ask me
Pyar kaise hota hain
How does love happen
Yeh pyar kaise hota hain
How does this love happen
Aur main sirf yehi keh pata tha...
And I could only say this much...