All I can tell you really is if you get to the point where someone is telling you that you are not great or not good enough, just follow your heart and don't let anybody crush your dream.
In matters of the heart it is always better to want something you don't have than to have something you don't want.
Real divas give 150 percent. If they don't have the right dress, they'll go out in whatever they have. If there are no microphones, they'll still put on a show. They are people who put their heart and soul in what they do.