As much as I try to pretend I'm not, I am a fairly impulsive person. I'm not blindly impulsive--I usually do have a head for consequences and implications of my actions--but I like to be able to make decisions based on the circumstances at any given moment. I like to be infinitely adaptable.
This is a quality that drives James (as well as others, I'm sure) crazy, perhaps with reason. I can imagine how it's difficult to deal with an impulsive person. First of all, there's just the unpredictability of it all. Will I come home after work, or will I decide at the last minute to take the super long way home that keeps me away for an extra hour or two? I know I said I would make dinner tonight, but now that it's nice out, I'm feeling like a trip to the farmer's market might be in order instead. Like I said, I try to keep consequences and implications in mind--I don't want to impulsively hurt someone's feelings, or destroy someone else's plans--but I can see how it would still be frustrating, especially because it's really easy to put myself and how I feel at any given point way ahead of anyone else.
Secondly, there's the theory that when I act impulsively instead of taking my time to puzzle out the right course of action, I'm more likely to make a wrong decision. That could be a wrong decision simply in the sense that it leads to an undesirable outcome, or it could be a wrong decision in the morally wrong sense, like if a decision I made impulsively led me to, oh, I don't know, contribute to the deforestation of Brazil or something.
That theory isn't actually all that compelling to me, though. An occasional undesirabely-outcomed decision is, I think, a totally reasonable pride to pay for the freedom of decision making. And as far as the morality of impulsive decisions, I think it falls into the same realm as keeping consequences in mind when making decisions. If I'm clear on what my morals are, I won't impulsively make a decision that violates them.
Even though I often feel like I shouldn't be, I think I'm basically a huge fan of impulsiveness. I think it keeps me on my toes, keeps things interesting, keeps me from falling into too much routine. In some sense, impulse is a childish thing, and it helps me feel like I haven't lost that sense of wonder, experimentation, and joy that kids have and that gets beaten out of them as they get older. I only feel bad about it when confronted with that unwieldy real world voice, the voice that tells me to grow up, be responsible, think of my obligations, blah, blah, blah. It's the same nagging voice that tells me I can't be a real grown-up without having set plans and patterns and goals and routines.
And honestly, I'm not sure how those two voices--the impulsive and the responsible--play together. I don't think they're mutually exclusive, but I feel like they're often seen as such. Which is (I think) why people are so threatened by impulse.
I say embrace it, though. Figure out what you will and won't do, and then give yourself as much freedom to make as wide a variety of decisions as you possibly can.