Can I just give up on being Christian?

I am getting tired and weary and I just want to give up on God. I know the scripture says to be still and wait upon him. I don't think I could anymore. At the same time, I am afraid to give up on him, because what if God is real and my grandma said " YOU ACCEPTED CHRIST AS YOUR LORD AND PERSONAL SAVIOR, AND I SEE YOU HOLDING ON FAST TO HIS WORDS DURING YOUR TIMES OF TRIALS, SO YOU BELONG TO HIM. ONCE HE STARTS HE WILL FINISH, SO HOLD ON A LITTLE WHILE LONGER" I feel comforted but still is it really worth it I ask myself everyday. What do I do? I can feel my faith slipping little by little.