David H.’s Answer
Forgetting your lines happens to every actor sooner or later. Being out on stage in front of a live audience is dangerous. It requires tons of rehearsal and preparation and concentration. It is also incredibly exciting. Also, you're not alone out there on stage, even though it may feel that way at times. Not only do you have your fellow actors to rely on, you have the audience on your side as well. They are rooting for you, especially in moments of distress. It's scary to forget your lines, but the play must go on, and it usually does. In live theater mistakes happen all the time. Theater is a complicated business and there are all sorts errors that occur during performance. Props, costumes and scenery, lighting and sound cues can all break, fall off, miss their mark, fail to turn on or ignite, but Onward! As you gain experience you will learn to roll with the punches, to deal with mistakes and sometimes to turn them to your advantage. And you will never forget them, and, if they are truly apparent to the audience, neither will they. All you can do is to work hard during rehearsal, stay focused during performance and do your job as best you can. You will find that you learn from your mistakes, which, unfortunately, you must make in front of a live audience.