No, you're not immortal. You've just got something deep down inside of you that won't give up, that refused to die. Maybe it's so small that it's more a gut feeling, a reaction, than anything, but it's there. What is this thing you hold within you? Hope, the reluctance to give up.
With life, there is always hope, no matter how small and insignificant it may feel. Hope cannot be squashed, smothered or destroyed, it's like a teensy tiny spark, barely a flame, but it's always there, ready for you to kindle it with your dreams and allow it to grow into a roaring fire, full of warmth, light and strength to keep you afloat.
Never forget that.