I've said before that not everybody is going to enjoy jiu-jitsu, but for those that do it often goes the other way... so many people absolutely love jiu-jitsu, but why? I don't think people love it because of the benefits, although they no doubt help. What I believe hooks most people are two things; the camaraderie amongst the team and the never ending challenge.
Lots of people end up training jiu-jitsu four or more times a week and most people train at least twice a week, that's a lot time spent with the same group of people and so it's natural to become good friends with those people. I have hundreds of friends who I know very well and I get to spend loads of time with, how can that be anything other than awesome? You don't just go training and learn new techniques, you have a laugh and banter with your mates the same time. This is another reason I like to keep lessons as informal and relaxed as possible. Basically, jiu-jitsu classes are like a night out with your mates but instead of wasting money on getting drunk you get to improve your life and learn how to beat people up... just joking... partially ;-)
Then the other part of jiu-jitsu which is awesome is that it never gets boring. There is always something new to learn, from a totally new sweep down to a tiny grip variation which improves a guard pass or tightens a submission. You can always try new things in training, I don't believe anyone could ever perform every technique a human body is capable of. Plus there is the performance aspect to this... unless you are an elite world class competitor there are always going to be loads of people better than you who you can aim to catch up with. I've been training for over eight and a half years (the last three full-time) and there are still plenty of people in the UK who can smash me... Braulio Estima makes me feel like a first day white belt. So when I know the level of ability that is possible I always have something to aim for, there is no end point.
Now that I think about it, there is probably a third reason... when you are training it's hard to think about other stuff, you become so in the moment while rolling. So any stresses or worries you have are forgotten for the time you're training, and quite possibly afterwards too. This isn't really a big factor for me because I don't let myself stress or worry about anything anyway.
I absolutely love jiu-jitsu and can't wait to get on the mats tomorrow. If for some reason you're reading this but don't train, give it a go. If you do train, do it more. If you used to train but stopped for some reason, stop being silly and get back to it!