I used to know a woman who called it "perseverating." I used to date a guy who called it "obsessive." I'm not sure what it is, but I get really into whatever it is I'm... into.
Cases in point:
I sew clothing. Sometimes from a pattern, sometimes not. At times I've stayed up all night because I was so impatient to try on a dress. I got the shakes over the coat Shirley MacLaine wears in The Apartment, and just had to have my own - with a dress to match the lining.
I knit. I've stayed up all night knitting, too. I've gone to conventions, mapped patterns, and given myself a wrist injury. Knitting. Yes. I blamed it on work, but everyone knew it was the knitting.
I run and bike. Earlier this year I decided I'd like to bike to work. Not every day, just now and then. To know that I could. The problem is, it's 18 0r 19 hilly miles each way. But I did it - and still do it, now and then.
Now I spend hours trimming pixels from invitation proofs. More on that later.
Meet DJ, the guy who puts up with me. He doesn't seem to mind - maybe because he's obsessive about his own hobbies right there with me.