Becuase death is fearful and death is sorrowful. You know when you visualise that someone died being agonised, murdered it realy brings sorrow in every human being. Worse in the case of Jesus Christ being murdered for the penalt He didn't deserve.It becomes joyful in us because knowing that the agony of death is no longer required of us the sin bearers,the penalt has been paid and Our God Father when looking at us is now seeing His sons and daughters, sure it is joyous. Praise God for His Beloved Son Jesus Christ who bore our sins on the cross of Calvary. For bible says, For God so loved the world that He gave His only begotten Son that who so ever believeth in Him should not perish but have everlasting life. This is the joy that feels us. To God be the glory forever and ever. A-A-A-Amen!