It also helps to break a monologue up into pieces (this also helps you to better understand what the author was trying to say and in what progression). Break it up into logical chunks that address a particular 'feeling' or 'topic' and then start the next chunk when the thought in the narrative moves on to the next topic.
THEN connect the two chunks by finding the association that brought the author to the next point they wanted to make...this way you'll remember which chunk comes next (though this isn't usually a problem).
This allows you to focus on a chunk at a time and get it down.
ALWAYS run the lines with the 'chunks' in the order in which you will say them onstage so you don't get confused.
Hope this helps.
"Life is a lesson in humility"