As John transitions from his introduction, he stops to encourage his listeners to stick with him because of what God has already done in their lives.
1 John 2:12-14
12 I am writing to you, little children, because your sins have been forgiven you for His name’s sake.
13 I am writing to you, fathers, because you know Him who has been from the beginning. I am writing to you, young men, because you have overcome the evil one. I have written to you, children, because you know the Father.
14 I have written to you, fathers, because you know Him who has been from the beginning. I have written to you, young men, because you are strong, and the word of God abides in you, and you have overcome the evil one.
New American Standard Bible: 1995 Update (La Habra, CA: The Lockman Foundation, 1995), 1 Jn 2:12–14.