In work environment, you gotta be reliable and smart. The thing is, there is always someone who is smarter than you. In fact, there's a chance that you'll have to manage someone who is smarter than you.
It's fine to be terrified. That's normal.
From what i've experienced, scope of life is so wide and one can't be smart at everything at once. One can be good at
x and suck at
y, and another person can be very great at
z but meh at
a. What i found to be useful is one should be really good at certain areas, then make him/herself to be integrated to the institutional knowledge. A person can be so good at something but in the end one that manage them all is person who's embedded to the institutional knowledge and align with the goal of the entire organization.
On top of what i mentioned above, don't forget about office politics as well. This doesn't mean you have to be yes-man of your superior; This means understanding that something doesn't just happen just because it is simply the best idea there is. You need to understand people's motive and make their interest align for something to happen and still be kind while doing it; You can do it dirty and you can do it by being very very kind and useful it is clear for everyone that your sole motive is for the overall good of the organization. Choose the later.