Good can't be one thing while what makes us reasonably happy is something else. If what comes first isn't good, then what follows can't be good either. For the second thing to be good, the first thing must be good too. But you wouldn't say this if you're thinking straight. If you did, you'd contradict both Epicurus and your other beliefs. So you're left with this: the soul's pleasure comes from bodily pleasure. And those bodily things must come first and be the real nature of what's good.
for good cannot be one thing, and that at which we are rationally delighted another thing; nor if that which precedes is not good, can that which comes after be good, for in order that the thing which comes after may be good, that which precedes must be good. But you would not affirm this, if you are in your right mind, for you would then say what is inconsistent both with Epicurus and the rest of your doctrines. It remains then that the pleasure of the soul is in the pleasure from things of the body; and again that those bodily things must be the things which precede and the substance (nature) of the good.