Jesus wanted His followers to have rock solid certainty to face whatever the future held
There is the certainty of His risen Life; by 10 appearances and many convincing proofs over 40 days.
There is the Certainty of who He is; the promised Messiah, the very Son of God and only Savior, the Good Shepherd who lays His life down for His sheep.
There is the Certainty of the Provision; the forgiveness of sin By God and eternal life with God by believing, repenting and receiving Jesus.
The Certainty of His unseen, but very real ongoing Presence. Jesus was conditioning His followers with the last 5 appearances over 39 days; to walk by faith, not by sight.
The Certainty of the Lord’s desire and ability to use us despite our failures. Jesus forgives Peter and then with confrontational love accepts Peter’s feeble lesser love and commissions him despite his failure.
The Certainty that the Risen Christ who stood before them would soon be within them; the greatest certainty of all, the eternal intimacy of us in Christ and Christ in us, just as Jesus was in His Father and He is in His Son.
The certainty of Jesus conditioning us as He did them; Jesus is preparing us for perhaps a great awakening or even His soon return, which should motivate us to avail ourselves for His mission, purifying ourselves.