How do you know what you know?

The question “How do I know what I know?” is another way of saying, “How do I know I exist?”. If this world isn’t reality, then it must be some kind of dream that we are dreaming from another place. Going on that principle, I think that what we are living in is real. The reason I think this is reality is because when I am dreaming, the world is completely different. When I am dreaming, I can do whatever I want, I can control events that occur, I can’t feel emotions or states of being, if I take a good hit to the face I wake up, if I fall I wake up, and if I sleep for too long, I eventually wake up in the middle of my dream. Of all of these reasons I think that the one that shows the most that this isn’t a dream is “I can’t feel emotions or states of being”. After a long and arduous swim practice, I will occasionally will dream about swim practice. I swim in it forever and unlike when I am awake, I don’t get tired after a few laps, I swim on an Olympic level rivaling Michael Phelps. If this was a dream, our lives would be completely different.