For me It is this song from Shin Shinaki Boobla Boo (1952). The Main reason is the lyrics which reminds me of love lost forever. The lyricist of the song is the movie’s director P L Santoshi ji whose love for the movie’s lovely heroine Rehana was not reciprocated and He wrote it for her. This is an image of the bubbly actress.

She migrated to Pakistan some years later and went away from limelight soon after. Here is audio of the song (movie is lost unfortunately).

First part Is mehfil version sung by the composer C Ramchandra which I prefer followed by the Lata original.

Here are it’s poignant lyrics:-

Tum kya jano
Tum kya jano
Tumhari yaad mein
Hum kitna roe
Hum kitna roe
Rain guzaari taare gin gin
Rain guzaari taare gin gin
Chain se jab tum soye
Hum kitana roe

Kitni kaliya khili
Chaman mein
Khilke phir murajha gaye
Birahan ke is
Bhole mann ko
Baar baar samajha gayi
Roke jawani kaati jisane
Roke jawani kaati jisane
Preet ke bije boye
Hum kitna roe
Tum kya jano
Tumhari yaad mein
Hum kitna roe
Hum kitna roe

Kitne baadal ghire
Gagan mein
Ghirke phir na barse
Pyaas bujha kar
Dil hi dil mein
Kitna tadape tarase
Dard hamara dil jaane ya
Dard hamara dil jaane ya
Naina khoye khoye
Hum kitanaa roye
Tum kya jano
Tumhari yaad mein
Hum kitna roe
Hum kitna roe.