You don’t know how to ______ because you’re just a ______!!!
This one is not actually a rule. It’s a bad attitude that some people have. First impressions are important and people have a hard time believing that you can do two things. If a producer met you as a PA, then you are a PA. If they see you next time as a Gaffer, they will be skeptical.
Everyone wants to hear a simple story. When your career transitions from one position to another that story can be confusing. You were telling a simple story “I do this job and I’m good at it.” Suddenly, you started telling a completely different story, “Oh actually, I do this other job sometimes. And I’m good at it. And I still do that other job. And I’m good at that one too. I do both.” That is too confusing! No one believes you can do both!
Even if you are good at two totally different things, people will be skeptical. (*Warning: Sarcasm ahead*) Oh, you’re an actor and you take good photos??? Yeaaa… right! Oh, you’re a make up artist and you produce your own music videos??? Sure you do! I bet they are… interesting. Oh, you’re an actor/director/producer/musician/model/cinematographer/marine biologist/editor??? I’m sure, you’re great at all of those things. (*end of sarcasm zone*)
But, in reality, you can do both! You need to simplify your story: “I do this new job now”. Unfortunately, you might need to make all new contacts because of “Film Set Rule #5”. Be ready, it takes time to transition, but with patience and good planning it will happen.