Mistakes are almost always of a sacred nature. Never try to correct them. On the contrary: rationalize them understand them thoroughly. After that it will be possible for you to sublimate them.
You have to read scripts and audition and develop relationships. It takes a long time to develop a body of work but over the last 25 years I guess I've done that many movies. In hindsight it may seem effortless but there's a lot of work that goes into it.
