If you dream of being the lead actor (or actress) and forgetting the lines, it means you are unprepared for your role. In real life, you may be facing a responsibility that is bigger than what you normally handle. This dream is a warning. You need to pay attention, to make extra efforts to doing your work.
If you don’t think you’re given shoes that are too big for your feet, then maybe you’re anxious over your duty and your stress triggered this dream.