To start, the "light healing potion" was never a recommended potion to use in the dark world. It was supposed to heal up a total of 60 life points. For knights, 60 might not be a lot, but it was plenty for saving the life of a sickly prince like Prince Horace.
Abel was steady when he took the dagger out of Prince Horace's wound. If he were just a little shaky, the blade would've scraped against the heart and do unrecoverable damage. That being said, the potion still managed to take effect as soon as it was consumed.
Prince Horace opened his eyes, drowsily, "Where am I?"
King Ambrose was about to cry, "You're awake, Horace!"
"Father!"
Tears started falling down Prince Horace's cheek. It was the first time that he had experienced something this dangerous. The thought of almost being dead made his emotion become very unstable.