He held on to the idea of that childhood, then imagined what it would feel like to kill the man
who took it away.
Hammer back.
Arm straight and steady.
He practiced in his head so he could do it right in person; but even in his mind, the gun shook and
was silent. Gideon had imagined the same thing a thousand times on a thousand nights.
His father was not man enough.
He would not be man enough.
Pressing the barrel against his forehead, he prayed for strength, then walked through it again.
Hammer back.
Arm straight.
For an hour more he tried to steel himself, then threw up in the dark and hugged his ribs as if all
heat in the world had been stolen, too  

what does "hen threw up in the dark and hugged his ribs as if all
heat in the world had been stolen, too" mean?