There is no such thing as unlimited capacity. High capacity people often accomplish much, which can lead them to believe they can accomplish everything. This can eventually take them to a place where they say yes to so many things, their quality of work starts to suffer.
Understanding limitations can be frustrating and empowering at the same time. You can't read all the books that are written. You can't complete all the work today. You can't build relationships with every person you meet. This is a good thing, as this limitation applies to everyone else too.
The books you decide to read, the work you decide to do, and the people you build relationships with are going to set you apart from everyone else. Stop trying to do everything and focus on the work that really matters to you.