Haha, it's a beast isn't it? Pick one and go with it, say how you have tired to improve yourself in that area you have stated. Don't try to make yourself look too bad though, always spin it in a positive light. Good luck
Sometimes honesty could be refreshing. After all, everyone knows the spin your flaw as actually a positive and everyone and their mother can do it it decently. A nice honest answer might actually surprise a person in a good way. Riskier, cause it means you have to stand out of the crowd, but could benefit you.
I mean, when you see this exact same thing in every TV show...you know it's become a little tooooooo standard of a response. Like in the Office when Micahel interviews for a new position and the CFO asks:
CFO: "What are your best traits?"
Michael: "well, why don't I tell you my worst traits. I work too hard. I care too much. I need things to really be perfect."
CFO: "Okay, so what are your good traits?"
Michael: "Well, you see. My bad traits actually are good traits."
Definitely don't choose your worst trait to talk about, but an honest reply might actually not hurt you.
For example...I might say.
I need to exercise more. I don't run or do enough cardio. I guess I always make up excuses for not doing it.
or
Even though I know it's not healthy, I still eat Campbells soup. I buy a few every week cause I know there will be times when I wake up late and just need to boil up something fast and eat before work and I don't have time to cook a healthy meal.
or
I always wait for the last minute to buy gifts. I know it's stupid, and sometimes I'll see my reminder notes and my PDA will flash at me "Buy Nicole's Birthday gift" a week before her birthday. But I still find ways to forget and get waylaid, and then it's the day before and I'm scrambling to figure out a gift. And I go online and look and find some great ideas, but there is no way to get it in time and I run out to stores and look around, kicking myself the whole time for not just ordering something online weeks earlier that would have been better. I still do it...I don't know why.
Granted...these are all inane, minor bad traits...but they're real. No excuses. No I'm too much of this which is really not a bad thing at all. No, this is how I'm already trying to change this flaw, so look at me...aren't I a good little self-improving junkie. It's just plain old flaws.