Effects Of Hit Point Damage
Damage doesn’t affect you until your current Hit Points reach 0. If you take damage to your Hit Points equal to or greater than the Hit Points you have remaining, you are reduced to 0 HP, and you’re knocked unconscious and dying (see below). It doesn’t matter how many Stamina Points you later regain (see Recovering Stamina Points on page 251) if you’re out of Hit Points. You can’t be reduced to fewer than 0 HP (however, see Massive Damage below).
For example, suppose Navasi has 17 HP and 1 SP. She takes 12 damage, is now at 6 HP and 0 SP, and can function normally. On the next enemy’s turn, that enemy deals 15 damage to her, reducing Navasi to 0 HP. Navasi falls unconscious and is dying.
Source
Core Rulebook pg. 250