When it comes to martial arts training, it's very easy to fall into the trap of thinking that what you are doing is all that matters; this, even after decades of mixed martial arts demonstrating that it's pretty important to broaden your training horizons to include a little more breadth and scope.
Even though specialization is mostly tried and true, it can come off a little shortsighted if there aren't some additional elements there to keep it honest. Authenticity in training or the pursuit of any goal, really, is what allows you to achieve more than just the minimum standard--it makes you a better person to have around because you are modeling behaviors that others can emulate. You become a role model and mentor, a compatriot and peer, and a person of a depth and quality. Authenticity of character is a powerful thing.
To that end, it's important to approach training holistically--make yourself more useful by stretching yourself, therein creating a near perfect training environment for yourself and those around you. But it can't only be about martial arts, or a single art; you do this by having a system, having a sport, and a specialty. Your horizon broadens and, with it, so does your ability to improve. Doing this is is the quickest means I know of becoming better than average and greater than good.
At life, I should add; not just martial arts.
Have a System:
Doesn't matter what it is, but try to choose something credible. BJJ, karate, tae kwon do, a dedicated self-defence program...doesn't matter, but have one and stick with it. Boxing, kickboxing or wrestling work here too, but only if you're not actively competing in them anymore. I'm not going to explain why, they just don't count if you're still competing; the dynamic changes enough that it stops being viable when wins and losses influence the art.
Have a Sport:
Get out and play something. Competition will keep you honest and the myriad benefits of being in something competitive will extend far into your personal and professional lives. You owe it to yourself. Boxing, kickboxing or wrestling work fine here, but only if you are actually in regular bouts and not perpetually "in training." At a certain point, it's okay to admit that fight sports are fun, but not your thing; switch to ping pong and reap the benefits of competing in something. Anything. I mean it--find something fun and go play. It's worth it. Playing a sport once or twice a week won't hurt your martial arts training, but it will definitely make you view it differently.
Have a Specialty:
What are you good at? And I mean really good at, not passably good at. Anything? Why should people take you seriously on any topic at all if you don't stick with anything long enough to have some insight into it? And no, an opinion doesn't count as insight. Everyone has an opinion, especially when they have access to their favorite search engine, but very few have insight. When you specialize in something, you become intimate with it; you can not only see the beauty there, but you can also see the limitations and ugly truths of your specialty. Dedicating yourself to a martial art is what turns it into a martial craft, and you into a craftsman.
So, how did you do? Do you have all three?
Sure, you can be the person who does BJJ, competes in grappling, and specializes in it, too. I can't even say that is the wrong approach depending on your goals in life. But what I'm hoping you take from this article is that you can do BJJ, play ultimate frisbee on Sundays, and can list 19th century impressionist painters in alphabetical order because that's something you study in your spare time. That first guy is interesting in the gym, but the second guy is who you hangout with at parties; the latter is more interesting and probably better at life just by dint of having a little more scope to his worldview.
In business, they talk about m-shaped versus t-shaped versus i-shaped employees and the value of each. It looks like this:
When you look at your martial arts training, what do you see? Are you i-shaped? Do you practice TKD, for example, and nothing else? Is that optimal? Maybe, maybe not. What would happen if you opened up your scope? If nothing else, it would give you some perspective that you might otherwise lack from the singular view of the world through your TKD lens.
Same thing applies to any martial art or sport combative. A little breadth, i.e., becoming t-shaped or even m-shaped if you can swing it, in your approach could make a dramatic change your life and your skills, even though it isn't always readily apparent how in the beginning. But cover those three areas off and all of sudden, people see you in a different light.
You have what is known as "utility"; even those who see it in you can't exactly define the whys and hows of it but they will appreciate it. You will be a leader and an exemplar of what training can offer when it comes to self-improvement and being a better person.
And isn't that the point?