Bear with me through this stock conversation:
"You wanna shoot some baskets?"
"Not really, I'm not any good at it."
"So is that a no because you don't want to, or is that a no because you 'aren't good' at it?"
Let's stop it right there. Chances are you've had variations of this conversation yourself, sometimes you are the "Hey, you wanna" let's do this or that thing person, sometimes, if we're honest, we're the bet-hedging reluctant party. Whenever we are the reluctant party, if the activity in question is something that we simply do not want to do no matter what our perceived skill level is then the negative answer is perfectly honest and reasonable. Outside of duty one should never acquiesce to any activity, endeavor, or conversation large or small that does not appeal to them. To engage in a voluntary activity that is contrary to your tastes or desires (again outside of duty) is to betray your reason, to needlessly limit your freedom.
But... if the activity is indeed something that we do have an interest in but we hesitate or do not participate because of a perceived lack in ourselves, then we are betraying ourselves and behaving irrationally. When we skip doing something that we would actually like to do simply because we "aren't good at it" we must remind ourselves how does one "get good" at something? Well, just like an infant learning to walk, one must actually "do" the activity in question to gain experience in it to "get better."
We must also remind ourselves when we say we "aren't good" at something, the next question should be "Compared to who?" In the opening example of shooting baskets the dialogue did not include "I asked Lebron James to shoot baskets with me but he declined; how about you?" In that case, you could state that in comparison your skills don't stack up to LeBron, but you're still game all the same. If the person asking the question were an uncoordinated 4-year-old I doubt the "I'm not good at it" excuse would be proffered.
When we decline anything we would like to do on the basis of our skill we deny the fact of "you must do to get better" and we fail to pass along whatever arbitrary internal yardstick we are referring to when we state whatever our current level of "deficit" is.
These two rules of thumb are mighty useful in trivial areas, shooting baskets for example, but they are all the more important in weightier matters. If we want to be good people, just people, morally sound people we must exercise these qualities, these traits in matters small and large so that we "get better" at being better people. And in these instances of import there is nothing wrong with keeping an exemplar in your mind as a moral yardstick. Whether your yardstick is Marcus Aurelius, Christ, Albert Einstein, or your grandfather it does not matter. What does matter is that you make your efforts at being the person you want to be even if you occasionally fall short of your exemplar's standard.
Epictetus provides us with a beautiful lesson in exemplars in his discourse "How, Upon Every Occasion, to Preserve Our Character."
"The highest greatness and excellence perhaps belong to others, to such as Socrates. But why, then, if we are born with a nature like his, do not all, or the greater number, become such as he? What, are all horses swift? Are all dogs sagacious? What, because my gifts are humble shall I neglect all effort for myself? Heaven forbid! Epictetus will not surpass Socrates-granted; but if I do not lag behind him that is enough for me. I shall never be a Milo, and yet I do not neglect my body; nor a Croesus, and yet I do not neglect my property; nor should we stop any effort in despair of reaching the highest."
Spot on! We must do, we must try, and if we do not measure up to the exemplar it will not be because we did not try. Trying and doing are the key and we discover the key to how to try in a lesson from Machiavelli's The Prince where we find this positive gem buried in what is mostly pragmatic cynicism.
"Men, walking almost always in paths beaten by others, and following by imitation their deeds, are yet entirely unable to keep to the ways of others or to attain to the power of those they imitate. A wise man ought always to follow the path beaten by great men, and to imitate those who have been supreme, so that if his ability does not equal theirs, at least it will savor of it. Let him act like the clever archers who, designing to hit the mark which appears too far distant, and knowing the limits to which the strength of their bow attains, take aim much higher than the mark, not to reach by their strength or arrow to so great a height, but to be able to with so high an aim to hit the mark they wish to reach."
The key then is to have exemplars as your yardstick but not to use them as excuses to not do as you will never equal them, but as goals to walk toward.
You may very well miss a basket occasionally but missing a basket while trying to make it is always far better than missing it because you never shot at all.