What was, I need, what is isn't

I had the world
Now I lay curled
And cold
I have lost nothing to outside observers
But in my heart
There is a void
And you were the only thing that could fill it, but now things are
Not looking the best for me,
When you left
You took my heart with you,
But maybe that's for the best
I will be in eternal misery
For the rest
Of my life
But I'll get used to it,
Because even if I was able to recover, find a new heart
Next time it walks away from me, I'll probably just keel over and die
When I told you I would love you forever, I never lied
But I almost wish I had
Because now I know it's true
With certainty
And now I'm in for a lonely eternity