That's pretty much the definition of what happens to one's feelings when one tries to dull the pain in one's life, isn't it? When you minimize your pain, over time, your pleasure goes with it.
Gosh -- how many times have I heard people who are under treatment for various disorders complain that seeking relief through medication that dulls the mind or the senses is not worth it to them? I feel sure they don't mind the dulling of the pain, but when the dullness also makes it impossible to experience joy, that's the rub. I feel the same way many times when I take too many antihistamines!
This exchange points out how important it is to emphasize that Epicurus was not about dulling the senses or emotions in general (sort of like the Stoics get accused of, whether rightly or wrongly) but instead increasing the one while decreasing the other.
So that's an important point in regard to dulling the senses from an overall perspective.
For purposes of debating the finer point, though, I suspect a different set of people, who would not themselves endorse dulling *all* the senses, would nevertheless be attracted by the idea of trading "joy" for "tranquility" because they have a definition of tranquility that to them does not imply dullness. So that's a somewhat different point. I'd like *both,* but if forced to choose between the two as part of some logic game, I would be more inclined to choose "joy" at the expense of "tranqulity."
So articulating how joy and tranquility fit together is an important part of articulating the Epicurean perspective, which of course reminds me of that passage from Torquatus:
[40] XII. Again, the truth that pleasure is the supreme good can be most easily apprehended from the following consideration. Let us imagine an individual in the enjoyment of pleasures great, numerous and constant, both mental and bodily, with no pain to thwart or threaten them; I ask what circumstances can we describe as more excellent than these or more desirable? A man whose circumstances are such must needs possess, as well as other things, a robust mind subject to no fear of death or pain, because death is apart from sensation, and pain when lasting is usually slight, when oppressive is of short duration, so that its temporariness reconciles us to its intensity, and its slightness to its continuance. [41] When in addition we suppose that such a man is in no awe of the influence of the gods, and does not allow his past pleasures to slip away, but takes delight in constantly recalling them, what circumstance is it possible to add to these, to make his condition better?
or from Cicero:
Cicero, In Defense of Publius Sestius 10.23: “He {Publius Clodius} praised those most who are said to be above all others the teachers and eulogists of pleasure {the Epicureans}. … He added that these same men were quite right in saying that the wise do everything for their own interests; that no sane man should engage in public affairs; that nothing was preferable to a life of tranquility crammed full of pleasures. But those who said that men should aim at an honorable position, should consult the public interest, should think of duty throughout life not of self-interest, should face danger for their country, receive wounds, welcome death – these he called visionaries and madmen.” Note: Here is a link to Perseus where the Latin and translation of this can be compared. The Latin is: “nihil esse praestabilius otiosa vita, plena et conferta voluptatibus.” See also here for word translations.