Some mental pains that I can imagine are anxiety, worry, desire for revenge, fear and anger. I know that one of the basic goals of Epicurus is to reduce or eliminate fear/anxiety/worry in humans.
I am using the terms Rational Decisionmaking and Rational Behavior Decisionmaking in place of the term Hedonistic Calculus. Section 18 is an attempt to describe Hedonistic Calculus, how one would make behavior decisions using criteria that align with Epicurean philosophy. I don't like the philosophical term Hedonistic Calculus because the word hedonist makes me think of eating grapes off a tross while participating in an orgy, and the word calculus reminds me of difficult to understand mathematic concepts, when in fact the term Hedonistic Calculus means a careful choice of behavior to maximize one's joy and happiness.
You can see in the original section 18 I used a mathematical explanation, or a spreadsheet explanation of hedonistic calculus. After reflection, I don't like this explanation, it is not the way I make decisions about my life. That is the reason for the rewrite of this section.
Either the English language is failing me with words to describe what I mean, or perhaps I need to find better words to describe things like "Present Moment Physical Comfort Enhancement". That phrase is clumsy and not quality writing. I could remove the word Physical which would reduce the clumsiness and make it less specific. One could write an entire book on the hedonistic calculus, and I am trying to describe it in a few paragraphs.