I am a Christian but also a nihilist

Imagine someone gave you a brand new Toyota Rav4 which is commonly accepted as a very good vehicle, it is functional, it has some safety features, good fuel economy, etc. The car is yours to do what you like with however if you break any of the rules of the road you will spend the rest of your life in a miserable prison. The person does not demand but wants you to provide them with daily letters of your gratitude for the car. Is this a gift or a curse??

This is effectively my perspective of life, it is commonly accepted as a "good" thing however none of us asked for it yet there are consequences for not using it correctly. Ecclesiastes 12:13 says "The end of the matter; all has been heard. Fear God and keep his commandments, for this is the whole duty of man." For me this purpose does not justify a lifetime worth of existence.