Stress

Stress is the short term stressed effect of seeing Zombie close by, hearing banging at your Door or other unsettling Noise, and generally anything which stresses you out (which will likely include annoying Survivor in the future). If nothing is stressing you out your stress level begins to drop. However, while you are stressed it will start dragging your Morale down, which is a more long term effect and harder to change.

Stress can be lowered by killing Zombie (ultimately this would depend on the personality of the Player), drinking Booze, taking some Painkillers, or smoking some Cigarettes