how to balance ego and humility?

I have always struggled with a big ego. This has been something I've been trying to improve within myself. I have always renowned myself as a very smart and talented person. The thing is, because of how high my standards have become for myself and for others, average seems awful for me. I can only aim for the highest. Anything lower and I'll deem it a failure or a sign of stupidity. Now, I've already realized this about myself years ago. What's become a problem is how I try and solve it. I try and reduce how quick I am to judge and instead doubt myself first, but then it results in me never having a conclusion because I fear that I'm wrong. This affects my daily life in so many ways. I'm constantly uncertain and at times it affects how confident I am in myself. I have trouble expressing opinions because, again, I am scared that I might be wrong and then receive judgment. Still, there are moments where my ego suddenly rises and sometimes I feel like I am the greatest person in the room. I always remind myself that I'm most likely not the greatest, though. I want to be confident, but not to excess. I want to be humble too, but not to the point where I am timid and easily used.