It's natural to fear death, not only because we can't see beyond the grave, but because God put within us a deep instinct to fight against death and keep on living. If we didn't have that instinct (which we share with all living creatures), we would ignore sickness and pain and danger, and eventually all life would cease.
But we were not meant for this world alone. We were meant for heaven -- and heaven was meant to be our final home. Heaven is our destiny, and heaven is our joyous hope! Death is a reality -- but Jesus' death and resurrection for us assure us that sin and death and hell have been defeated forever. We don't need to fear the grave, because by His death and resurrection Jesus has opened heaven's door for us.
When fears come, turn your mind and heart to Christ. When pain and exhaustion become your daily companions, thank God for the hope we have of heaven. Think of it: If you know Jesus Christ, some day you will be safely in God's presence forever! Never forget: "Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me; thy rod and thy staff they comfort me.... Surely goodness and mercy shall follow me all the days of my life: and I will dwell in the house of the Lord forever" (Psalm 23:4, 6, KJV).