You are always sniffling and carrying some kind of light disease. You never really seem to be entirely healthy. Not only may this affect your physical status but it can also make you tired and more sensitive to exhaustion.
Every time that you would gain Stress, you gain an extra point. (If you were to gain 4 Stress for a march, you instead gain 5.) The trait is also to be used in the physical save when trying to resist a disease, or when you are rolling to resist Stress.