There's a saying that I think is really great, and I use it every chance I get.
It's this one:
It's an expression of the attitude of worrying about your own business, and not worrying so much about the business of others.
You are responsible for YOU - your own circus, your own monkeys.
This is especially true in the martial arts.
Of course we depend on our teachers and training partners to work hard, study well, and be competent and trustworthy when we work with them. That's a given. And sometimes we do have team-effort activities, like group kata in competitions.
But that's not the rule. In the martial arts, success or failure depends on one person.
What we do in the martial arts, at its most basic level, is a 100% individualistic endeavor.
Our progress, with few exceptions, depends mostly on us, and just us. Not only is it a matter of natural talent (we all know those people who are physically gifted) but it's a matter of hard work, plain and simple.
There are lots of aspects of our study we can't control. We can't control injury or when/where a bad guy chooses to offer us violence, for example. But so very much of what we do is totally up to us.
Studying the martial arts is one of those activities where our own effort counts more than anything else. We don't have to worry too much about team work, about whether or not the others are working as hard (or harder) than we are, or whether someone else has done their part enough so that we can be successful in what we do. We can't "lose" martial arts because someone else didn't do their part.
We can't depend on other people to "cover" us if we fail, either. No matter the martial art, if we're having an off day, or we haven't practiced, or we aren't doing what we're supposed to do, it shows and it can't be blamed on anything else.
This is one of the more powerful aspects of the study of the martial arts. People who stick tend to develop a sense of personal responsibility for their own success and the habits to make that success happen. This is why I think we tend to see kids in the martial arts excel in academics, other sports (including team sports) and activities that require a lot of skill and practice (such as playing musical instruments).
We're our own team coach, captain, and cheerleader.
We're on a team of one.