There is a wealth of resources out there that cover over-indulging, the inability to say no to that extra serving. There is much out there about the proper way to abstain and how to acquire the virtue of fasting. I may even touch upon these later. However, for now, I am considering spiritual gluttony: that is, to say, the inability to say no to sin.
Yes, gluttony is about the flesh; it is when fleshly pleasure conquers will. Fleshly pleasures involve the taste, and touch. Nevertheless, I think gluttony can extend to not saying no to certain thoughts, and behaviors. We may be gluttonous over a certain day-dream and try to always escape there. Or we may be gluttonous insofar as we are addicted to a tv show, sports stats, video games, gossip, to talking constantly, drinking, sleeping or finding unhealthy outlets to pain, and responsibility. We over indulge in things that take us away from God, our spouse, our family, our faith. We may know that there are limits to how much we should indulge in distractions, if at all, but we just can't resist doing it, saying it, thinking it, participating in it just one more time.
This is different than greed, because greed covets and seeks to have more for more sake, whereas, gluttony seeks to experience a pleasure and/or to escape pain because the body wants to inordinately be in a state other than what it is in. When our will is weakened by these addictions, whatever they may be, I feel that St. Thomas' definition of gluttony still holds:
"Gluttony denotes, not any desire of eating and drinking, but an inordinate desire... leaving the order of reason, wherein the good of moral virtue consists."
It is an inordinate desire leaving the order of reason, wherein the good of the moral virtue consists. While it is most manifest in the appetite, can we admit gluttony in other areas of our lives, maybe the secret part of our lives? If so, when are we going to stop? When is enough, enough? When will it be the last time?