When Meliodas got out of the crystal prison he was trapped into, he is in a half-conscious state using his demon powers on instinct and giving a hell of a fight.
I thought he was in this state because the power was overwhelming. However, this theory seems to have been proven futile.
Later its made clear that Meliodas can handle even greater power if he taps into his demonic and was mainly restricted by his conscience not to hurt innocents.
So, why exactly was he in that kind of state at the time? Has this been explained in the manga (or anime) at some point?