I used to do ju-jutsu (german, not brazilian) for 4-5 years, but I quit about a week or two before I would have had my exam for blue belt....completely lost my interest and couldn't be bothered to go on for that last couple of weeks to get the blue belt so I ended up with a green one, which I don't consider to be anything really.
I mainly lost interest because there were no competitions in german style ju-jutsu, only brazilian and I didn't like that one bit, boring matt wrestling. Now thinking about it I think it was a bit stupid for me to quite since I was pretty talented and would now be really good at it.
I have been thinking of starting either Krav Maga or Kung Fu for two years now, but tennis has been taking my time for the past year or so. I love martial arts, but it is very time consuming if you want to actually get anywhere with it.