The dreaded "mental block," can strike at any time, even with songs you know well, and just because you've written the song yourself doesn't make it easier to remember the words. Learning other people's songs is a doddle by comparison. You usually learn other people's songs by listening over and over again, and as someone else said, writing the words down helps assimiliate it too, but with your own songs you don't have that luxury of being able to listen again and again.

For a wee while, one particular song I've written, "The Faery Glen," really bugged me. I'd sing it at home and it was fine, I'd sing it at the local folk club and always stumbled at the last two or three verses. I sang it at another folk club, and at quite a big venue locally and it was no bother. Mind you, it is twelve verses long.

The best advice is sing it again and again and again ....