Man, it's very difficult, and very humbling to try and wrap your head around just how big the universe is. I don't think human brains are capable of thinking at that scale.

We actually don't know how big the entire universe is in reality. When people talk about the size of "the universe", they talk about the part whose light has reached us, the visible universe. What's beyond is pure speculation. Also, due to the expansion of space, large parts of even the visible universe are inaccessible to us. Even if you started today at 99% light speed, you wouldn't ever reach them.