You have experience in melee combat, while on the edge of your life.

If your HP are reduced under 25%, rounded down, of your maximum HP (up to a maximum of 25HP):
You regenerate 1 temporary HP, whenever you take an attack action. You cannot regenerate that temporary HP if you are unconscious.

If you have 7HP or less, not counting temporary HP, and you make a melee attack, you get 7 - your current HP as bonus damage of the attacks damage type.