Imagine you want to do something other than what you do for a living now. For example, you are an engineer, but you want to be a painter, or maybe you are an actress, but you want to be a rocket scientist. Will you do it? Will you just stop everything and try the new thing?
All too often I hear my friends tell me they want to, but they won't because they are not experts, and because other people have more training and more experience, my friends must not be good enough. Nonsense!
The society is structured in a way where other people make you believe that you cannot do something because you don't know enough. Think about it, when you grow up, the society puts you on a path of learning, that culminates all too conveniently in a single profession, that you ought to do for the rest of your life, because that's what you are good at. And everything else? That's for other people to do, because they are experts.
Does expertise matter? If you want to be a surgeon, you better be a highly educated doctor with a lot of experience. You don't want me to pick up a scalpel and start exploring your insides. But if you want to start acting, for example, then you just need to start acting. Sure, you'll make a fool out of yourself, but who cares, no lives will be endangered. The truth is, it's not that hard to learn a new language, or a new skill, or to understand science or business or marketing ... All you need to do is to choose what you want and then go out and learn it. With internet, the resources are limitless.
Other people are just that, other people with their own desires and insecurities. They may know more or they may not, but that should not stop you from trying, from believing that you can do better. The only reason you are afraid to try the new thing is you and you alone.