It's a slow melody and the music will make you think it's a sad song. Actually, It's a very romantic ghazal from the Pakistani hit film Badal Aur Bijli (1973). Bangladeshi Actress Sabnam was the heroine of the film. Please check the song:

Lyrics urdu & English translation (In Bold): 

aaj jaane ki zid na karo

yoon hi pehloo mein baiThe raho

aaj jaane ki zid na karo

haay mar jaayenge, hum to luT jaayenge

aisi baatein kiya na karo

aaj jaane ki zid na karo

tonight, don’t insist on leaving.

keep on sitting close to me like you are.

tonight, don’t insist on leaving.

oh, I will die, I will be lost,

don’t say such things.

tonight, don’t insist on leaving.

tum hi socho zara, kyun na rokein tumhein

jaan jaati hai jab uTh ke jaate ho tum

tumko apni kasam jaan-e-jaan

baat itni meri maan lo

aaj jaane ki zid na karo

just think for a moment, why should I not stop you.

my life seems to leave my body when you get up and go,

I swear to you, my beloved

just agree to this request of mine

tonight, don’t insist on leaving.

waqt ki qaid mein zindagi hai magar

chand ghadiyaan yehi hain jo aazaad hain

inko kho kar mere jaan-e-jaan

umr bhar na taraste raho

aaj jaane ki zid na karo

life is trapped in the prison of time

but these are the few moments that are free

by losing them, my beloved

let’s not have a life of regret

tonight, don’t insist on leaving

haaye mar jaayenge, hum to lut jaayenge

aisi baatein kiya na karo

aaj jaane ki zid na karo

kitna maasoom rangeen hai ye samaa

husn aur ishq ki aaj meraaj hai

kal ki kisko khabar jaan-e-jaan

rok lo aaj ki raat ko

aaj jaane ki zid na karo

what innocent, colourful weather it is.

it is the peak of beauty and love today.

who knows what will happen tomorrow,

let’s stop this night, tonight,

tonight, don’t insist on leaving.

[Source: http://www.bollymeaning.com/2016/09/aaj-jane-ki-zidd-na-karo-lyrics...]