I'd say that a large majority of email that I read from aspiring actors states that if they only could (a) get an agent, (b) get an audition, or (c) get a break, they would become a success as an actor.
Of course such beliefs are on the level of urban legend. They are just rumors that are repeated by the hopeful. I will explain why these three beliefs are not only untrue, but antithetical to becoming a success as an actor.
Belief #1. An agent will make you a success as an actor. Actually, sometimes an agent who is really enthusiastic about one of his talent may help that actor get auditions and roles that lead to the actor's success when the actor has what it takes to be successful. But it is not an agent's job to make people into actors. Agents make money from people who already are actors, people who can get roles when they are sent to auditions. Until you are an actor whose experience and training and personal qualities are such that you can get roles when you audition, an agent cannot help you. Then, another thing often happens to aspiring actors once they get an agent: they sit around waiting for the agent to call. An actor who is going to be successful can never do that. He always has to be acting and networking. There is much to do besides waiting for the agent to call. This also leads to the idea that many in the industry have and that is that an agent is the last thing and actor needs, not the first thing.
Belief #2. If I got an audition, I would become a success as an actor. Professional actors know that one audition is unlikely to get you a role. In most cases it takes a great many auditions to get a role. A great many actors are vying for every role. To get a role, you have to be what the casting director is looking for from the actor- you look the part, you act the part well, you have the background that indicates you can be trusted to do the part well. Besides, there are darned few open auditions for speaking roles. Most people who audition for a role get the audition through their agent. Those people are actors with considerable experience and training and who have the qualities needed for being an success.
Belief #3. If I got a break, I would become a success as an actor. Much is made of actors getting 'breaks' that make them successful. Such 'breaks' are being cast in roles that get them noticed by their fine work. Except there is more to it than that. Besides the actor's fine work, is his look, and charisma. These things have been important in getting the actor his agent and the agent sending him on the audition for this role. Then they are important in getting the role.
Most actors who are "suddenly discovered" from a "breakout" performance have been actors for many years.
You see. There is no shortcut to success as an actor. It takes years to develop into the sort of person who can be a successful actor. It takes outstanding qualities. Outstanding talent, experience, look, charisma, personality, training, etc, are all needed to be a successful actor.