As mentioned above, penalties are brutal. Being heavily encumbered (e.g. by armor or just stuff hauled around in case you need it) takes a toll on your success chances. In addition to that, heavy encumbrance also increases the rate at you gain fatigue significantly, which adds another penalty, and getting injured (doesn't matter if it was a lucky shot or not: the injury is there anyway) adds additional penalties. Through this, you can quickly have your success skill drop to the minimum, eventually making it impossible to move, and then pass out from the lightest of injuries.
Unless your character is a maximum strength giant Kaumo, you need to balance the protection of your armor against the encumbrance/fatigue rate of it, and you should drop all carried equipment you don't need in the fight (excluding at least bow and possibly arrows, as enemies can pick those up and use them against you).