dimaag ki to hai nahi
jaan loon ke jaan doon
main rahoon ke main nahi
If I listen to my heart, it's there.
If I listen to my mind, though, it's not.
Should I take a life, or give mine,
Should I remain, or should I not..
That's the simple, literal translation of the poetry that is actually Gulzar's version (I believe, it very well may be Vishal Bhardwaj's) of 'To Be or Not To Be' of Hamlet.
If you have an idea of the Hamlet, you can easily relate it to the scene in the movie, where Shahid has a gun in his hand and is asking 'jaan doon ki jaan loon', much like the confusion Hamlet of Shakespeare was in, in his soliloquy 'to be or not to be', while contemplating [or feigning, as the case may be according to one's interpretation] suicide.
The doubt whether it was actual contemplation of suicide or just feigning isn't cleared by Vishal in here as well, though my personal expectation is that the feigning part may be kept off from the movie.
[You may read more about the original 'Hamlet' soliloquy at Wikipedia Page.]