We can be sure of our salvation because our Savior is alive and He is God. The saving grace of God was wrapped in the unchanging love of the Father through the death of His Son- the Lord Jesus Christ. The shed blood is the river of love which flows from Calvary to humanity from generations to generations.
"25- For I know that my redeemer liveth, and that he shall stand at the latter day upon the earth: 26- And though after my skin worms destroy this body, yet in my flesh shall I see God: 27- Whom I shall see for myself, and mine eyes shall behold, and not another; though my reins be consumed within me. " (Job 19:25-27 KJV)