How do I know what I Know?

This is a question frequently asked by philosophers and other thinkers. Long story short, you don't. You will never be completely sure about anything. In a sense, it is a sad and unfortunate aspect. On the other hand, the uncertainty is a beautiful part of life. I admit I don’t quite understand people’s thought that they don’t quite know anything. I agree w/ Descartes that one is not deceived by their senses. For example, if I lay the ball up and watch it go through the hoop, I know that I watched the ball go through the hoop. There is no disputing that fact. I think that most people would agree with me, however I feel that most would also agree with me in saying that there are few things that we are certain about. I think that the hardest part of this argument is deciding where to draw the line.
How many stars are in the sky? How do I know if I exist? How do I know what I know? etc.... These are all questions that I don't think we will ever know the answer to. I think that most people agree with me on that. Basically, we don't know much of what we know at all.