Let In, Let Down

So this is how this has to end?
I thought you'd always be my friend
You took the better parts of me
Long nights of waiting by the phone
Cold silence never cut so deep
I guess I'm better off alone
You gave me your word when I said I would fall
And all that I needed was anything at all
I let you in, you let me down
I scream and you don't make a sound
I let you in, you let me down
Now all I want is just to know how you could ever let this go
I'm left with all that's said and done
Those empty words are all the same
I should've known what you'd become
Another year washed down the drain
The scars on my chest from what you can't undo
But what hurts me the most is I can't get over you
I let you in, you let me down
I scream and you don't make a sound
I let you in, you let me down
Now all I want is just to know how you could ever let this go
So this is how this has to end
I thought you'd always be my friend
But I guess you won't, and I can't forget
How everything was just a mess
When you were here, I couldn't breathe
I just kept drowning underneath
I let you in, you let me down
I scream and you don't make a sound
I let you in, you let me down
Now all I want is just to know how you could ever let this go
I let you in, you let me
I scream and you don't make a sound
I let you in, you let me down
Now all I want is just to know how you could ever let this go
Why did you let me go?