Like you did? Faelan thought, as he stood there panting, his hair fluttering in the aftermath of Harry's magical outburst. Is that why it's so easy for you this time?
Faelan had been ready to run, to flee, to find that accursed veil and drag Sirius back, or just to go, but Harry's stoicism, more than anything, deflated him where he stood. Harry had already accepted Sirius' death once, knew immediately how to do it again, and he knew -- he knew -- that it had to be killing the man inside. So, if Harry wasn't running after Sirius, then maybe...maybe Sirius couldn't be run after.
At that, all of Faelan's energy left him, and he sank to the floor, the letter that had still been clenched in his fist floating to the carpet.