When is the Mass not celebrated?

Now John's disciples and the Pharisees were fasting. And people came and said to him, “Why do John's disciples and the disciples of the Pharisees fast, but your disciples do not fast?” And Jesus said to them, “Can the wedding guests fast while the bridegroom is with them? As long as they have the bridegroom with them, they cannot fast. The days will come when the bridegroom is taken away from them, and then they will fast in that day. No one sews a piece of unshrunk cloth on an old garment. If he does, the patch tears away from it, the new from the old, and a worse tear is made. And no one puts new wine into old wineskins. If he does, the wine will burst the skins—and the wine is destroyed, and so are the skins. But new wine is for fresh wineskins.” (Mark 2: 18-22)

Jesus says the proper time for his disciples to do penance is when the bridegroom is taken away from the wedding guests. This will happen between His death and resurrection and the fast Jesus is referring to is the Eucharistic fast. That is why the Church doesn’t celebrate Mass on Fridays and Saturdays during Holy Week. Eucharistic fasting should also be done whenever we are not in God's grace, so let us try to increase our commitment to confession so that we are able to receive the Eucharist as often as possible.