Jesus preached: Greater love has no one than one who lays down his life for his friends (get reference).
Jesus practiced: He laid down his life for not just his friends but his enemies as well (Romans 5:10)

When one lays down his/her life for a friend, that love is deemed great. Then what kind of love is it, where one lays down his/her life for a enemy? Such love is far greater than great love.
We must practice what we preach as well just as Jesus did. While we were still sinners (enemies of God), Jesus died for you and me. He went beyond practicing what he preached. How about you/me?

Romans 5:8-10 (KJV)
8 But God commendeth his love toward us, in that, while we were yet sinners, Christ died for us.
9 Much more then, being now justified by his blood, we shall be saved from wrath through him.
10 For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life.

John 15:12-13 (KJV)
12 This is my commandment, That ye love one another, as I have loved you.
13 Greater love hath no man than this, that a man lay down his life for his friends.