Paul Graham wrote an article about what constitutes genius. Commonly, a natural ability and determination are ascribed to genius.
 

Genius = natural ability + determination

In his Bus Ticket Theory though, he argues that there are people who are obsessed with collecting bus tickets. They will be able to tell you all about those tickets. They experience joy when they do it, although their craft may be purposeless.

He further argues that all great geniuses have a bus ticket collector attitude towards their respective subject: Darwin was obsessed with natural history. Ramanujan was obsessed with mathematical series.

Contradicting to the beautiful narrative you can tell in hindsight, none of these geniuses had a grand master plan or vision to change the world. Leonardo Da Vinci didn't sit down and had the masterplan of painting the most known painting to date - the Mona Lisa. Einstein didn't sit down to use math to ascribe nature because he thought he could contribute to physics or become famous for his E=MC2.

They all obsessed over their topics because they simply couldn't help it. They were just really interested in solving mysteries in their respective fields and it is only thanks to their obsession that they could endure the pain, the struggles and the challenges along the way that defied other people to derive to the same results. After all, it is a marathon.
 

Genius = natural ability + determination + obsessive interest

Why is it important?

I think we all need a bit of a Genius and Bus Ticket Collector attitude when it comes to pursuing our goals and excelling in them. Whether it is to drive our own personal projects or building our own companies. There are a lot of good ideas and opportunities out there, but not all of them may be right for us to pursue. 

I think we must all trust our obsessions a bit more diligently. By pursuing our obsessions (rather than other things people tell us are good), we protect ourselves from breaking down mentally when times are tough. Our obsessions can help to energize us, even if we spend 24/7 on them. They keep us on our paths while a million other distractions tug at us at the same time like our bad conscious, our doubts or other external opportunities. And most likely, we can also only truly excel and grow beyond ourselves by pursuing things we deeply care about and obsess over.