As Lot and his family flee from Sodom and Gomorrah as it's being destroyed, Lot's wife looked back and was turned into a pillar of salt. Sometimes, we get caught up in things that cause us to turn back, look behind us, remember the past, and it only leads to our death. When we seek to preserve our life, and get caught up in things of this world instead of God, we actually lose our life. So, we remember Lot's wife... but we remember Christ's life even more, because of His past actions that we should look to.