Step-by-step explanation:
let's go on with the example, you study in 10th standard you are a very good student with good scores. One day, your friends present you a math problem from 11th standard.. Now you are being challenged and you accept to do it. You know you can do it because your IQ is higher than that of others. That's how you know that you know your ability.. your capability to do things.
but then your friend starts mocking you by saying you are an overconfident classmate. If..you get demotivated by that statement that your friend made..you will easily loose the test because you will just not have the good energy in you. But if you are positive and motivate yourself that you can prove them wrong that's how you know motivation determines what you do.
But what if you were overconfident about things that would make you go like heh i can do that.. but it will then go out of our expectations because you are not really prepared. So if you had the right attitude you could have done better right. and that's how you know attitude determines how well you do it.