Parents derive immense amounts of joy from discovering similarities between their children and themselves. There’s nothing cuter than a daughter who looks like her mother, or a son who acts like his father.
God is no different with His children. The more we inculcate virtue in our hearts, the more we resemble Him Who is the source of all virtue. And when God sees in us the image of His own Divine Goodness, He is so pleased that He offers us a share in His eternal happiness.
Let this, then, be the sole end of all of our actions–to become perfect even as our Heavenly Father is perfect.