Changing my belief about my ability to write fiction

I just listened to the “Beliefs” call with Brig Johnson (amazing call) and I realized that part of what is holding me back on my dream of being a mystery/thriller writer is the belief that I won’t be good at that type of writing because I’ve never done it before. (I am a writer, but I’ve only written content and journalism, not fiction.)

I know that looking to what I’ve done in the past isn’t going to help me here because it will just keep giving me the same results, but I have trouble believing I’ll be able to believe I’m a good mystery writer without any evidence that I can do it. The T that I won’t be able to do it creates fear and “confusion.” When I try to write, I freeze. I have the urge to Google “how to write a mystery” or to find a writing coach to teach me how to do it. I resist doing those things because I feel like I “should” be able to find the answers in myself.

How can I work on developing the belief that I’m good at writing mysteries before I write a mystery so I can write a good mystery? I wonder if maybe it would be better to do a ladder belief of I can be a terrible mystery writer and still write a mystery (that is my goal, I didn’t say it had to be good , but I want it to be good of course.) Another possible ladder belief would be something like I can teach myself to write a mystery. Thank you!