Losing only Grit means successfully dodging, block, deflecting, or otherwise avoiding an attack.
Direct Damage means an attack has landed, and has potential to cause serious injury. If an attack deals Direct Damage but the resulting Direct Damage Save is a success it only dealt minor harm that can easily be shurgged off.
Failing the Direct Damage save causes a Wound.
Unless otherwise specified Direct Damage is dealt to STR. In some circumstances mystical energies or psychic horror might deal Direct Damage to WIL, whereas attacks that seek to entangle or slow might deal Direct Damage to DEX.
In these circumstances make a Direct Damage Save as usual, but using the affected Attribute rather than STR.
A wound is an an actual injury or lasting harm, represented by stepping Attribute dice down from their Maximum size.
Wounds resulting in a die dropping below a d4, to zero, means incapacitation and risking serious consequences.
Taking Direct Damage or a wound to an Attribute at zero dice results in death.
When you have ten minutes to catch your breath and drink some water, you restore all of your Grit back to its maximum. Doing so in a dungeon or hazardous environment may expose the party to danger.
An incapacitated character can be gotten back to their feet with the application of simple first aid. This does not require any special supplies or specialized training.
First Aid takes 10 minutes and restores Grit, but no lost Attributes.
A night’s rest accompanied by food, warmth, and shelter recovers one step of Attribute loss from a single Attribute.
A full day’s rest in comfort completely restores a single Attribute to it’s maximum.
If you are without vital needs for a full day (food, water, rest) you are deprived and cannot regain Grit or Attributes.
Concentrating on a spell to maintain its effect also causes deprivation until it is ended.