I wrote this:

I don't have friends,
I've just got one.
This is the tale
Of how I have none.

Our story was great,
We wrote it together.
How long would it last?
I hoped for forever.

But Jim Moriarty
Came into our lives.
In the darkest hour
That criminal thrived.

He drove Sherlock mad,
And reeled my friend in
With puzzles and games
Sherlock needed to win.

The Final Problem
Led to the end.
The press called him fake,
My only best friend.

Moriarty tricked me
And Sherlock was stumped.
I watched from below
As my friend jumped.

He hit the ground hard.
Without further ado,
I ran to him, screaming,
"He's my friend, let me through!"

I couldn't believe
That Sherlock was gone.
Maybe it all
Was just one great con?

I said to his grave
All that I'd kept inside.
Except for one thing,
That I promised to hide.

One simple phrase,
I think that he knew.
My dearest Sherlock,
I love you.