In order to assist you in your performance and practice periods, it is recommended that you memorize your monologue early in the process.
During your memorization process, try not to memorize any lines in an “acting” voice or performance; try to keep it as neutral as you possibly can.
To assist you in this process, check out an enduring memorization technique all the way from Shakespeare’s time!
Another method, is asking a friend or family member to sit with you whilst you are practicing the memorized speech; they should be holding the lines and whilst you are reciting and you forget a line, you can try saying “line” to your partner and they can remind you the first couple of words.