Fatigue

Fatigue is a stat in DF, which determines your overall ability to do STUFF. Your maximum fatigue points can be calculated by multiplying your Constitution by your strength.

Your maximum fatigue can be reduced by losing health, and can only be restored by resting or druidic healing. Magical healing CANNOT increase your effective max fatigue. Some abilities, such as strength from land, allow you to overfill your fatigue. Fatigue can also be stored in magical 'fatigue batteries' which can be made by any competent enchanter or creative battlemage. Fatigue is almost always lost in transfer, though, so there is a downside.