Fwiw, here's my translation of that section:
The steady contemplation of these things equips one to know how to decide all choice and rejection for the health of the body and for the tranquility of the mind, that is for our physical and our mental existence, since this is the goal of a blessed life. For the sake of this, we do everything in order to neither be in bodily or mental pain nor to be in fear or dread; and so, when once this has come into being around us, it sets free all of the calamity, distress, and suffering of the mind, seeing that the living being has no need to go in search of something that is lacking for the good of our mental and physical existence. For it is then that we need pleasure, if we were to be in pain from the pleasure not being present; but if we were to not be in pain, we no longer desire or beg for pleasure. And this is why we say pleasure is the foundation and fulfillment of the blessed life.