the pure love of Christ
Having recently reached an age where I now attend Relief Society, I have spent some time pondering on its motto--a part of a scripture that is seen on the walls of every Relief Society room.
Charity never faileth.
I have come to understand that charity is an action. It is not simply feeling the pure love of Christ--that is impossible. Charity in its truest form is serving another because of love. Christ spent His entire life serving because of His great love for His people, for all of us. He served--and serves us still--because a love as great as His cannot be contained. He sees us in our truest form, and He loves us deeper than we can comprehend.
I don't think that it is possible to fully experience the pure love of Christ without acting on that love, without serving the recipient of that love. To feel something so powerful as charity is a gift from God. "Charity never faileth" because it is an action based entirely on the desires of God, and when God is at the center of anything it cannot fail.
Those who serve with charity in their heart serve with, and because of, and for love. They serve, not for attention, not for money, not for themselves, but for the Lord. They serve because of His love for His children, and they serve because they feel His presence when they do. They feel what He feels when He serves--they feel love.