Yesterday's wine may have been everything that the Lord promised it would be, but when He brings 'new wine' we can expect to encounter a change. The new wine will hold a freshness that will be able to stand on its own. It is not to be measured by its predecessor, regardless of how excellent that predecessor happened to be.
It does take courage to leave the old behind and embrace the new, but God's word is emphatically clear. If we put new wine in old wineskins we will essentially loose the good wine. (The old skins will not be able to hold the new wine, for through the process of fermentation the old skins have weakened over time).
When I ponder what Jesus spoke in the gospels of Matthew, Mark, and Luke regarding 'new wine', I have begun to understand more fully its meaning for me. The pharisees and scribes were tainted by their erroneous interpretation of God's word, and therefore were unable to receive the 'new wine.' To mix the fresh truths of God in with this thinking was not something that Jesus would do. He understood that for an individual to understand and implement the things He spoke of they would have to be born again.
Being born again of the Spirit would bring needed transformation to their spirit man. The old would fall away and the new would be in its place. Now the new wine would have a wineskin that would hold it safely.
2 Corinthians 5:17 KJV Therefore if anyone is in Christ, he is a new creature; old things are passed away; behold, all things are become new.