How to know if you are a god designer?

I've always wondered if I am a good designer or if there are a few good designs that made me think that I can do a good job. I recently discovered that my colleagues changed a design I made behind my back. They told me I did a good job, and after a few weeks, I noticed they completely changed the templates I created for conference certificates. There are other situations: I find it difficult to create posters or other commercial materials. The thing is that people like my personal projects, but when it comes to creating something for work, it's not always good enough. How can I manage this? Does it make me a bad designer?