I desperately want to work as a nurse again but there's something stopping me

I'm an RN in my mid twenties. One year after passing my final exam I quit my job. My life circumstances were really not that great. My mental health was even less great, even though I couldn't quite explain why back then. That was a few years and many therapy sessions ago. I'm doing much better and basically have my life way better under control. In the past few weeks I've been thinking about getting back into nursing. And for the first time, I've managed to express my mental health problem from back then:

I'm comparing me/my skills to everyone in my immediate vicinity. Constantly. At work that includes everyone from interns to RNs and Doctors (even though I know that that's very irrational and unfair). This leads to my self confidence fluctuating to an unbelievable amount. I have no intrinsic confidence in me/my skills. This probably stems from early experiences with abuse and neglect. In my work life I'm missing objective measurements to assess my performance better. Obviously I am talking about all this in my weekly therapy appointments. Still, it is very power consuming and I'm kind of stuck with finding a solution. I just know that I want to go back into nursing.

So I want to ask you all:

• What can I do to develop a sound and realistic confidence in my professional skills?
• What can I do to be able to evaluate my own performance without comparing myself to others?

Any and all responses are greatly appreciated and I thank you in advance.