Jesus speaks in the gospels about the problem of pouring new wine into old wineskins because the skins would break having already been stretched by the old wine. It is necessary to put the new wine in new skins so that the skin expands as the wine ferments in order to complete the product properly.
Neither do men put new wine into old bottles: else the bottles break, and the wine runneth out, and the bottles perish: but they put new wine into new bottles, and both are preserved. Matthew 9:17
Its no different with salvation. When we become sons and daughters of God through His glorious redemption, we must not attempt to use the old wineskins with the new ‘wine’ that God gives us. In God’s Kingdom, there is no space and no use for old wineskins. Jesus requires us to be completely removed from the old, to use the new wineskins of righteousness that God provides in the form of forgiveness from sins we have comitted and then grow in Jesus as the new wine grows in the new wineskins.
We have to surrender everything of our old life, “for the old has gone and the new has come”. Darkness has no place with light – We cannot be a part of God’s Kingdom whilst still carrying baggage from our old life – that skin is stretched out already and to attempt to use it will result in disaster. It is no use asking for God’s forgiveness only to try and put the new wine that he offers (new life) in our existing old wineskins of sinful life.
When we come to Jesus seeking forgiveness, we must lay it all out on the altar of repentance. We must lay everything of our old life before God and hand it over to Him to deal with it all and resolve to only use new wineskins for the new wine that God provides.