FalaAAallaka bakhiAAun nafsaka AAala atharihim in lam yu'minoo bihatha alhadeethi asafa (surah Kahf: 6)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(18:6) Well, (O Muhammad), it may be that you will consume your life for their sake out of sorrow, if they do not believe in this message. *4

Fala`allaka baakhi`un nafsaka `alaaa aasaarihim illam yu;minoo bihaazal hadeesi asafaa

*4) This refers to the real cause of the anxiety of the Holy Prophet at the time of the revelation of this Surah . It clearly shows that the Holy Prophet did not grieve at the persecution from which he and his Companions were suffering but at the deviation and moral degeneration of his people. What was consuming him was that, though he was trying to bring them out from their disgraceful state, they persisted in it. He was grieved because he was convinced that their deviation would inevitably lead them to destruction and scourge of Allah. Therefore he was working day and night to save them but it appeared that they were bent upon incurring the chastisement of AIIah. The Holy Prophet himself has described this state of his mind in a Tradition to this effect: "I may describe this thing in a parable. A person kindled a fire to spread light but the moths persist in falling over it to burn themselves alive. He vies to save them from the fire but the moths reduce his efforts to failure. The same is true of me and you. I hold you by your skirts to keep you away from the fire, but you are bent upon falling into it." (Bukhari, Muslim).
Though apparently it is merely stated "...... it may be that you will consume your life for their sake out of sorrow...." it also contains a sort of consolation for the Holy Prophet, as if to say, "As you are not responsible for forcing them to believe, why should you consume yourself for their sake? Your only duty is to give good news and warning and not to turn people into Believers. Therefore you may go on carrying out your mission of giving good news to the Believers and warning of the bad consequences to the disbelievers."