There has always been in survival an important defense mechanism called fear. Fear is an amazing motivator and can really open our eyes to what is around us. The problem in today's world is fear seems to be a bit misplaced. We use it to analyze ourselves instead of our surroundings. We allow it to cast self doubt, self judgement, and let it be our scorecard. Then there are those that just want to deny it even exist. I am not afraid of nothing. That just means you haven't met it at, if your being truthful.
I heard a collegue say that they were afraid they were doing the wrong things in their career, life and all those areas that come with life. The thing is not feeling the fear or even the self doubt it is when we allow it to consume what we are doing. A little fear is good for us. Makes us re-evaluate and maybe take a step back and see where we are at and that is all good. You choose a path because of a passion or a love of something, well you should do that but we don't always. If you love what you do then embrace doing it and let the other go. If your not getting the part or selling the script does not mean your horrible but maybe just not the right time. If you question your ability then pick up a class, go to a workshop but work on it. If your lacking somewhere then that is how you discover it. Seek out those things that you question and see if your right. If you need to fix something then start working on it. Don't give into fear but use it.
In acting, writing or any creative world you have to remember everything you do is subjective. People will love it, hate it or not even care. As a creative person you already do not fit the normal pattern of the world. So if you start doubting or feel your suddenly not good enough, I say sudden because you got into this because you love it, then go back to basics. Play with something out of your comfort zone or even do something you know for a fact your not good at and see how it compares. Usually you will find out that your strengths are a strength for a reason.
By the way I am not speaking from high on the mound. I am consumed with self doubt constantly and it is my classes and workshops that I go that make me feel better and more grounded. I get to identify what I really need to work on and what is just my self doubt. One of my biggest problems is I cannot watch myself. I have been able to a couple of times if enough whiskey is consumed. All I could see is what I did wrong. Bad thing. I had someone really put me to the screws one time when I was speaking out loud about how bad a job I do and they told me "How dare you spoil my joy of watching you work!". Wow! That stung. Just because you have self doubt does not mean your not good. It just means your human.
Keep in mind fear is a survival mechanism not a judgement of how accomplished you have become in your passion. Fear is a cue to go back to basics. Fear is a signal that we may need to push our boundaries. Fear is there for a reason. Fear is not there to destroy you. Fear is not there to crush your dreams. Fear is a motivator. Embrace your talent. Push the boundary. Explore. Most of all love what you do.