Noticed something that I don't think anyone else pointed out: you provide a causative link between a consequence of your behavior and your new-found desire to change it: it's hurting your business. I note this because most of the replies are approaching the question as though the source is a lack of empathy or an abundance of ego. While both of those seem, on the face of things to be true, they're really very broad, shoot-at-phantoms problems.

But one might approach the query from a different direction - you're terrible self-centered. Not in terms of ego, although you seem to have that in spades. Rather, this wasn't a problem for you until it impacted your own goals, probably pecuniary in nature. In short, you've concluded that OVERTLY being a dick doesn't pay. Like really doesn't PAY (business). But you clearly have a certain commitment to COVERTLY continuing to cleave to a sense of superiority, or else you wouldn't have tried to cling to any sort of justification for your past and present behavior.

In some ways, I think I can relate to what you're going through, because I used to be quite curt, and I'm still not what the average person would consider to be warm and fuzzy. I'd like to say that the answer for you is to form a rational basis for a new personality. But of course, that's like saying that the answer is to form a rational basis for the existence of the tooth fairy.

Truth is, my pointy parts and sharp edges didn't dull at all until I really got the crap kicked out of me in life a few times. There was a brilliant book (name escapes me, 1950s I think) that described the turning point for an alcoholic by saying something like, "The chronic alcohol abuser will continue to degenerate until he concludes to his own satisfaction that the pain of continuing to drink now sufficiently outweighs the pain of stopping."

I think you're on that path right now, personality-wise. You've noticed that there are certain costs to continue to be the way you are. Unfortunately, those costs are not nearly as high as the costs of changing, in your mind. Therefore, it is presently more valuable to you to stay as you are. When the reverse is true, it will become patently obvious what there is for you to do to change your behavior, as you actually already know approximately how to do it if you are even half as smart as I think you imagine yourself to be.

You will, as a matter of self-regulating, automatically begin asking yourself, "How will I come off if I say what I'm thinking? Is there a more responsible way of saying it? Is there even value in saying it at all?" I think you know that, though. I imagine you were hoping for something else.

Good luck!