Is a kind person born that way, or cultivated?

We all know that extremely happy and kind person that can't say a bad word... as well as that pissy and grumpy pain in the rear that grumbles at everyone and everything.

My questions is this: where they born that way or is that the result of lifes work?

I'm a happy and kind person in general, and I think I've been this way most of my life.  Not because of religion or upbrining (my Mom & Dad are pretty grumpy peple), but because I've always just had that urge in life.