If you have a propensity for writing and you can slay with your prose, consider writing an ebook. While the market has certainly become saturated as of late, books that help teach people about a technical topic still sell extremely well. This is a great source of passive income but does require a large amount of effort at the outset before any money is generated.
The ego is the driver making the decisions. It decides between the devil (the id) and the angel (the super-ego) on either shoulder (yes, all those cartoons you've ever seen are partly true). We have voices in our mind, and it's up to the ego to decide which one to fulfill. Its goal is to satisfy the id in some way while also attending to the super-ego.