I believe that John is taking us through all the stages of Spiritual life. We are children when we first believe and need the milk of the Word, being taught by the Word. Grow into young men, capable of understanding more, eating the meat of the Word. As fathers, we should have matured to the spiritual stature of being teachers responsible for giving back our knowledge and experience. Encouragement brings strength and confidence to our faith. John spplauds their overcoming, giving them confidence to press on.