If your Stamina bar under the Health bar is getting smaller that means your hunter is hungry and you should eat some food.

Eat Before Every Mission

There are some armors that can decrease the speed which your Stamina bar shrinks but you can't fully stop it.

You can make missions easier by eating something in your Tent before every mission.

• Go to Tent > BBQ Menu > Grill a Meal > Recommended Meal.