The context for this is Jesus being questioned about why He and his Disciples did not practice fasting. His told his critics that it was not the time for fasting. You don't fast at a wedding celebration.
Jesus was introducing something new, the fulfillment of God's promise. In Jeremiah 31 God promised a New Covenant with His people based on forgiveness, not the Law. Jesus brings the New Covenant. At the Last Supper Jesus called the cup of wine the New Covenant in His blood for the forgiveness of sins.
The New Covenant of Love and Forgiveness would not stay contained in the old, familiar ways practiced by Jesus' critics. Simple patches would not fix what was broken in Israel. The Gospel Message would break free to fill the whole world.