My month of asceticism having passed, and having had some time to relapse as the mood strikes me, I am able to draw some conclusions from the experience.
Caffeine - My relationship with caffeine has changed quite substantially as a result of my ascetic endeavor. I suffered pretty bad migraines for a day or so within a few days of giving up caffeine. The migraines subsided a couple days later and I was left heavily craving caffeine for about two weeks. By this point, more than a month after giving up caffeine, I still have some desire for caffeine but I feel as though I wouldn't have any trouble continuing indefinitely without caffeine.
That I could continue indefinitely without caffeine doesn't mean I plan to. I have no plans to relapse to my prior levels (2-5 units per day) of caffeine usage but caffeine can be quite useful so neither do I intend to swear off caffeine. My plan is to go without caffeine in general but turn to it at times when I find myself desiring of more wakefulness or other stimulants.
Caffeine only for a purpose, not out of habit.
High fructose corn-syrup - Adding high fructose corn-syrup to my ascetic month was a very good choice on my part. I have decided to entirely give up high fructose corn-syrup and I'm not looking back. Mostly, all of the things that I have to give up to avoid high fructose corn-syrup are not things that I mind giving up. I kind of miss soda a little bit but only just barely.
It takes a little bit of awareness and vigilance but I feel that it's worth the effort to go without high fructose corn-syrup.
Alcohol - Nothing much learned here. I still enjoy the flavor and side-effects of alcoholic beverages. Having had a month without alcohol has left me with a somewhat decreased tolerance, which has its pluses and minuses but that's about all that I've gotten from this month as regards alcohol.
I guess the fact that I drink alcohol because I enjoy it and not out of habit might be a valuable thing to have learned.
Drugs - Giving something up that you weren't going to have been doing isn't really giving something up.
Conclusion: Giving stuff up for a while can give you a new perspective or appreciation for the things that you give up. Sometimes that new perspective is that old habits aren't worth keeping.