Einstein was a super genius but that doesn't mean he never made any mistakes or that he finished everything he started. He believed that messing up was part of being successful. Einstein's mistakes and unfinished work, like those of many people, have proven valuable and have even led to new ways of thinking. Here's one example:
Imagine that you and six of your friends are in a pitch-dark room and feeling different areas of an elephant. You can't see the elephant, so you all think it's something different. If you're touching the tusk, you think the elephant's a hard, pointy thing; if you're touching the ear, you believe it's floppy.
Einstein spent the second part of his life trying to develop a "complete theory" that would explain all the forces and phenomena in the entire universe. He never finished it. Many believe that Einstein spent the last part of his life "spinning his wheels" working on this theory. Today, scientists see value in Einstein's idea and are still trying to come up with a "theory of everything."