I always thought this song was very appropriate for Sherlock.

Goodbye to love

I'll say goodbye to love
No one ever cared if I should live or die
Time and time again the chance for love has passed me by
And all I know of love is how to live without it
I just can't seem to find it

So I've made my mind up
I must live my life alone
And though it's not the easy way
I guess I've always known

I'd say goodbye to love
There are no tomorrows for this heart of mine
Surely time will lose these bitter memories
And I'll find that there is someone to believe in
And to live for something I could live for

All the years of useless search
Have finally reached an end
Loneliness and empty days will be my only friend
From this day love is forgotten
I'll go on as best I can

What lies in the future is a mystery to us all
No one can predict the wheel of fortune as it falls
There may come a time when I will see that I've been wrong
But for now this is my song

And it's goodbye to love
I'll say goodbye to love

...

Sherlock was fed up, fed up of feeling alone, of wanting someone. He was fed up of having feelings at all.

Because no-one was going to come; no-one ever does.

He was going to spend the rest of his life yearning for someone who would never come, and fending off the boredom the only way he knew how – with drugs.

He'd tried most of the drugs available to him – ecstasy, heroin, cocaine, alcohol, tobacco, and more; even custom made mixes. They only took the edge off temporarily before he was brought crashing down to reality. And Sherlock was sick of it.

He now fully recognised how unlovable he was, how no-one would want him, could want him, even as a friend, never mind anything more. He began to believe that he was one of the accidents of the universe – everyone had someone to love, or was loved by someone, or had friends or family, or even a pet. But Sherlock had none of them – he refused to believe his family cared for him – and felt he had no place in the world.

He lifted his glass in a bitter toast "to the world, to life, to love", before gulping down some tablets, washed down by the strange concoction. Then he lifted the syringe and injected its contents into his already prepared arm. Two other syringes followed, and he sat back on the sofa, waiting for the numbness to come, then the darkness. Sherlock knew his heart had died inside him, and that his body only had to follow.