"Love like this cannot be fully understood."
Christ died for us, for our salvation. He died for people who would reject Him and His love over and over again. Think about how many people throughout your life who have rejected you. Would you die for them? Would you even die for somebody you "loved". The answer is probably "no" to the first question and "maaaaaaybe" to the second question. Yet, here is a man who died for you and for me. How many times have you rejected Him? I'm not going to lie, I have several times. Even as a Christian, I have rejected Him. We reject Him when we lie, gossip, ignore His calling in our lives, when we choose to be selfish instead of giving, and the list goes on. We reject him all of the time yet Christ died for us and loves us THAT much. Love is Christ.
"Nor can love like this be earned."
This gift from God is free. Eternal life for believers is not something to be earned. Only faith can get us there. Works will not give us eternal life.
Loving like Christ means loving when it is not being returned, loving imperfections and flaws, and being God's instrument to love others.
"In His love and in His mercy He redeemed me." Isaiah 63:9