Ye safar bahut hai kathin magar

dil naa ummiid to nahin, naa-kaam hi to hai
lambi hai gham ki shaam, magar shaam hi to hai - This part of the song is from a poem penned by Faiz Ahmed Faiz (I think). The poem is also included after the lyrics for the song.

ye safar bahut hai kathin magar
na udaas ho mere humsafar

ye sitam ki raat hai dhalne ko
hai andhera gham kaa pighalne ko
zaraa der is mein lage agar, na udaas ho mere humsafar

nahin rahnevaali ye mushkilen
ye hain agle modh pe manzilen
meri baat ka tu yakin kar, na udaas ho mere humsafar

kabhi dhundh legaa ye kaaravaan
vo nai zameen naya aasmaan
jise dhuundhati hai teri nazar, na udaas ho mere humsafar

The Poem

karte hain jis pe ta'an, koi jurm to nahin
shauk-e-fazool-o-ulfat-e-nakaam hi to hai.

dil na-umeed to nahin, na-kaam hi to hai
lambi hai gham ki shaam, magar shaam hi to hai.

dast-e-falak mein, gardish-e-taqdeer to nahin
dast-e-falak mein, gardish-e-ayaam hi to hai.