I can tell cause I'm going through stopping. Secret is to drink less every day. If you stop completely you feel like death, you cannot sleep, you get nightmares when you do, it's just a bitch. Physically, your belly bloats, as your liver gets bigger. Your body knows how to process alcohol better than food, so anything you eat gives you diarrhea, makes you gassy and uncomfortable. You look puffy and tired in general, over time a sad or angry looking face sets in and you start noticing people are staring at you or are intimidated by you. Low production of serotonin (I think) will make you overly sensitive, quick at anger, feel like breaking down and crying, low attention span, bad memory. I've seen people "too far gone" and I don't have the medical knowledge to tell you about it. But for the average 6 pack a night/one bottle of wine and half a pot of coffee high functioning alcoholic, it's more about the escapism of it, being in a situation you hate, and it's kinda easy to break out.

If you're the spouse of such a person, do not nag them, or blame them, show love and patience. Negative environment will exacerbate it.