dawn,

You need to commit your lines to memory so they are second nature. If you have to think to say them, you will be more likely to struggle. The term is 'over-learned skill.' An over-learned skill will be much more able to be recalled during times of stress.

A drama teacher put it this way, You can not give away your lines until you make them yours first. This is all the more important for those of us with memory/cognitive issues.

My best to you.