The first kind of humility is to hold my brother to be wiser than myself, and in all things to rate him higher than myself, and simply, as that holy man said, to put oneself below everyone. The second kind is to attribute to God all virtuous actions. This is the perfect humility of the saints. It is generated naturally in the soul by the performance of the commandments. It is just like a tree bearing much fruit: it is the fruit that bends the branches and lowers them down, but when there is no fruit, the branches point upwards and grow straight.
There are certain kinds of trees which never bear any fruit as long as their branches stay up straight, but if stones are hung on the branches to bend them down they begin to bear fruit. So it is with the soul. When it is humbled it begins to bear fruit, and the more fruit it bears the lowlier it becomes. So also the saints; the nearer they get to God, the more they see themselves as sinners.