At the Last Supper, Jesus explained that the wine He gave the disciples to drink was to remind them of His blood. Though they didn't realize it at the time, very soon thereafter the blood that He would spill in the Garden of Gethsemane and on the Cross would help pay the price necessary to wipe out everyone’s sins. Because He paid the price, those who repent of their sins can be forgiven, as if those sins never happened. Thanks to the Savior’s atoning sacrifice, we do not have to remain separate from Heavenly Father when we die, but can go home to Him, and go home clean.
Speaking of clean, when we are baptized, the water symbolically washes away all of our sins just as the blood of Jesus actually did. When we partake of the Sacrament, our first priority is to remember and appreciate the Atonement of Jesus Christ. We also are to be reminded of our baptismal covenants. In August 1830 Joseph Smith was warned not to purchase wine for use during the Sacrament service, but for the Latter-day Saints to make their own wine or to use some other drink, instead (see D&C 27).
Today in our Sacrament Meetings you will find we use water to represent the Savior’s blood. For me, using water during the sacrament of the Lord’s Supper, I’m reminded not only of the Precious Blood, but of the water than cleansed me when I was baptized and personally covenanted to always follow Him.