He would never admit to anybody just how much he missed him.

Through his long and lonely mission, taking down Moriarty's Network, he would think of their reunion, and find the courage to go on. He thought of the warmth he provided, the confidence he instilled by his mere presence.

Mycroft had better be keeping an eye on him, he would think in his darkest moments. Even if I didn't explicitly instruct him to, he knows better than it let him come to harm. Or he will suffer the consequences.

When Sherlock was rescued from Serbia, he inquired about him, right away. He would only feel at home once they were reunited. Mycroft played dumb, as if he didn't understand the significance of having him in his life.

Luckily, Anthea was a smart girl. She brought him back to Sherlock. The detective felt his heart warm as he was reunited with Woolly, his favorite Belstaff coat.