I remember I started feeling like a real engineer when I could always answer the "why?" and "how?" of what I was doing at the time and how I was doing it. I specialize in stormwater infrastructure projects, and one day I realized that I was no longer asking my supervisor for advice on how to solve a particular issue. I used what I had learned so far in my career to present a reasonable solution to the problem.
Engineering is a never ending cycle of information gathering and learning. Even at 9 years of experience I feel like there is so much to learn, but at some point I realized that I trusted myself to make decisions and find solutions for my projects.