We love because He first loved us. (I John 4:19 ESV)
The root of becoming externally focused is understanding Christmas.
You know the basic Christmas story: Mary was told by an angel that she would carry God's Son. She and Joseph eventually traveled to Bethlehem, where they found nowhere to stay but a stable. That's where Jesus was born, and He was soon visited by shepherds who had been told by angels about the birth of the Christ child.
But how often do we think about the Christmas story from God's point of view?
God the Father forever existed with His Son, Jesus, in loving fellowship. But something was wrong. Sin had invaded God's creation, and the people God had created no longer experienced the earth, their lives, or God Himself as He had intended.
So God sent, and God went: God the Father sent His Son. God the Son went to earth.
But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. (Galatians 4:4-5 ESV)
In a much more difficult trek than going downtown, "across the tracks," or even around the world, Jesus left the peace and pleasure of heaven to visit a place far less comfortable. All to serve and save the people beyond His home.
God also sent angels to tell the shepherds the good news. He sent a star to guide the wise men, so they too could worship. Even before that, God sent Gabriel to tell Zechariah about John's birth and Mary about Jesus' birth. He sent an angel, too, to help Joseph understand Mary's pregnancy.
God the Holy Spirit also went to fill in John the Baptist and enable Him to prepare the way for Jesus. And the Holy Spirit went to inform Simeon and Anna that the baby in Mary's arms was the Awaited One.
God sent, and God went.
...who, though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, by taking the form of a servant, being born in the likeness of men. (Philippians 2:6-7 ESV)
In other words, there would have been no Christmas if God Himself didn't have an "external focus." If God didn't see the need, move beyond heaven to meet that need, and reach out to tell about His work to others, there would be no gospel and no salvation.
But we have a God who sees, sends, tells, and goes. We serve Him by doing the same. That's why we're an "externally focused church" - because of Christmas.