Someone once told me an instrument is a remarkable outlet for one's emotion.

[ He looks at the violin he's "borrowed" for this mission. Sherlock never played an instrument with Jon. He never learned when they still had the chance to.

Once Jon was no more, Sherlock played and played until mastered the instrument. He clung to the music when everything else in his life, all that he had known had shattered. Sherry and Jon had become Sherlock. Just Sherlock. He was alone. More alone than he had ever been. ]

Maybe you need to play it until you find yourself peace. That is, if you still want to play.