Core

Cores are a feature in Red Dead Redemption 2 that are an extension of player attributes, kicking in when the corresponding attribute has been completely depleted. Core icons are located inside their associated attribute meters.

The level of the core will also reflect how quickly players will recover those attributes; i.e. the higher the level of the core, the quicker that attribute will replenish. Health and Stamina replenish naturally over time, but Dead Eye is dependent upon kills.

Maintenance
Cores naturally drain slowly over time, taking a full 90 minutes to deplete completely. Adverse conditions will affect this rate of decay, including weather and fighting. Actions that counter fatigue and hunger will counteract this, such as eating and sleeping.