Use a letter to tell your son that you love him and are proud of him. Write specific reasons why your relationship with him is very important to you and how you hope to continue to grow closer.
In the first part of the letter, tell your son that you love him unconditionally. Let him know that your love is not based on anything that he can do or achieve, but is given to him freely and without limits. For example, say, "I will love you always, no matter what happens."
Follow up by telling your son how proud you are of his accomplishments, talents and abilities. If he excels in academics or athletics, be specific about a particular goal he worked for and met. If he is kind or generous or has a unique social skill set, praise those attributes in him. For example, say, "I am really proud of how much you give to everyone around you."
Next, write about all the ways you value a relationship with your son. This is a good opportunity to tell him the ways you hope to improve things, such as spending more quality time together or learning to understand each other better. Remember it is not appropriate to use the letter to criticize your son or accuse him of any shortcomings. If you have any shortcomings or anything to apologize for, this is the perfect time to apologize or make amends.