Why should the words, "This is my blood of the covenant, which is poured out for many for the forgiveness of sins" (Matthew 26:28) fill us with sorrow? Why should they fill us with joy?
Visualising in my mind to the moment our Lord Jesus said the verse to the disciples, inevitably it fills me with sorrow knowing that the only man without sin has to pay the price for my sin and the sin of everyone in the world. The suffering on the cross that Jesus had to go through as a result of our sinful nature adds to our repentance and our gratitude to Him.
The same will also fill us with joy because we know very well that Jesus has paid the penalty and able to redeem us from the evil one. We have the assurance of forgiveness and eternal life through Christ Jesus. The word "many" in the verse gives us more assurance that Jesus has not only redeemed the Jews but gentiles like me as well.