A' Is No Longer Available

From point 'A' to B.
To C what D has instore for you.
With a running back and forth,
Trying to find someone willing to stay in place...
As a means to satisfy your convenience.
But I was that 'A',
You ran from to be with B.

And after finishing with C...
You believed D,
Would provide you all your needs.
And you found yourself with an empty E.
Only with an F you...
Have earned to learn,
'A' is no longer for you available.