When God chooses you, He keeps you eternally secure in His hand. The child of God is saved by Faith, and nothing you can “or can’t do” will change that. No action can change your eternal state. When you become born again, nothing in earth or hell can change that.
Who can undo the work of God in your life? Of course the answer is NO-ONE. Cease from your dead works of trying to save yourself, rest in the finished work of CHRIST!!