Most importantly, he understands you. He understands you and me.
Sherlock: Most importantly, he understands you. He understands you and me.
Watson: What do you mean by that?
Sherlock: I mean, Watosn, whether you care to admit it lately or not, I am an important part of your life. Whether I say it out loud or not, you are an important part of mine. My return to New York was driven in large part by my desire to repair our relationship. I think even though we might draw further or nearer from each other, depending on circumstance, you and I are bound, somehow. Andrew accepts that without feeling needlessly threatened. It's a rather enlightened position.