Boy, if those are the most regrettable things you've ever done in your life, then you've lived a pretty good one SBH!
Opening your figures is never a bad thing. Personally, I can't decide whether collecting carded is better than loose or vice versa. But I do know that I love my loose collection.
Dressel Rebel's solution: I buy 2 of each figure (except army builders which usually amount to 15+ of each). One to keep carded, one to open.
from me on this!
As for the most regrettable thing I've ever done... Hmm, can't really think of what that would be at the moment. Probably just being a total pain in the butt teenager to my parents for a good number of years, constantly making them worry about where I was, what I was up to, when I'd come home, if I was going to get into trouble, etc...
That, and ever watching The Phantom Menace