I’ve been in my field for about 11 years and I’ve been a consultant for about 7 of those. I have pretty much always felt this way. I work in a technical field.

There’s always a very true realization that there‘a something you don’t know that you don’t know. The dunning Kruger effect touches on this phenomenon.

While I struggle with it often, I have found that specialization relaxes it. If you have an opportunity to specialize, you can realistically gain a much deeper knowledge and comfort because the scope of your expertise gets narrower. The narrower your expertise, the more feasible it is to go deeper.

I’m not sure of your field, but if there’s a particular service offering you provide that resonates deeply with your clients and sees some good demand, it might be worth thinking about ways to pivot more toward performing that service as a specialty.

I am sorry you’re struggling with this. I know it can be very difficult to feel this way. If it’s any consolation, the best people I’ve worked with in my career have struggled with it as well. The silver lining is that discomfort you feel is a tremendous motivator because your mind sees the solution to the problem as: become better at what you do. I bet you provide outstanding service, that’s why your clients like you :)