On martial arts, I think people need to participate in one focused on contact to know what it's like to get hit. It's impossible to train the pain management and mental will to continue fighting INTELLIGENTLY while injured unless you actually experience the pain. This is why I would recommend supplementing any strike/flourish art like Tae Kwon Do with something straightforward in this respect like boxing. Also, an art like hapkido or certain jiu jutsu focuses will train one to make practical grappling choices.
I am always weary of submission based arts because, if there is more than one attacker, you can't expect to lock up with one person - this will get you killed. This is why striking should be primary, followed by joint manipulation and body mechanics (throwing). A "fight" is a situation of either life and death - throwing punches at some guy for talking shit while drunk is not what martial arts are for.
In any case, Tae Kwon Do is greatly accessible as well as limitless. If you want to be deadly, the tools are available. If you're just looking to get some exercise, it's great as a health hobby as well. Be prepared to memorize a few things as per the discipline side, but there's no minimum in terms of physical prowess. To the best of your ability, as they say.