It's been said over and over again to give 100% in everything that you do.
I'm not sure I entirely agree. After all, 100% implies a finite resource.
If you are truly giving 100% in everything that you do, you are going to be completely exhausted.
Instead, I think to be great at something, sometimes secondary matters require a lesser degree of attention and effort.
For example, let's say you are a world-class chef. You are a master at crafting delicious meals and can wow anyone's taste buds. You give this 100% because it's your passion, and people recognize you for that.
One day, you decide to go into business for yourself. Now instead of giving your passion 100%, your attention is spread around also operating the business. You have administrative tasks, marketing concerns, accounting, the list goes on.
Now instead of focusing 100% on being the best chef in the world, you know find yourself becoming a mediocre chef and a sub-par business person.
You are spread too thin, and your core suffers.
Pick what truly matters and give that 100%.
Outsource the rest.