Remind me, again, why I'm doing this?

Four days without Diet DP.  I have a mild headache, which is my body's way of saying "something's missing here.  Shouldn't we usually have about 40 milligrams of caffeine in here by now?"  (40 milligrams just sounded good, I actually have no idea how much caffeine is in the average soft drink).  The headache I can deal with.  The cravings are driving me crazy.  I like water, but I'm not sure how much more of it I can take right now.  So I have been drinking lemonade and milk.  Can we say "calories"?  Arrgh.  Which makes me really start to question the wisdom of going off soft drinks at all.  I know they're not good for me, but gaining back thirty pounds isn't going to be good for me either.  Neither is eating half a package of Chips Ahoy cookies and a glass of milk.  (Ahem.  Monday night.)  I don't know if I can handle eating fewer treats/snacks AND giving up my DP.  I feel like I can only really focus on changing one thing at a time.   If I have to have a vice, wouldn't a non-caloric one be better?  Should I keep going and see if it gets better?  Should I fall off the wagon in favor of focusing on another health issue?   I really don't know what to do here.  I'm open to any and all opinions and advice.