At least there is usually some forgiveness for folkies who lose their place. In an orchestra the instruction is - 'I don't care if you are dead; your bow will still go up and down in time with everyone else's! '
But I can have a tune in my head all day, going over and over it; then when it's time to play, the tune goes and hides, usually half way through.
I can only reiterate the advice given - practice. Speed, and accuracy, are different things, don't try for both at once. And most important IMPROVISE. Get your fingers used to following your thoughts. If you get stuck in a performance, make something up that fits. The brain will drop back into the right gear eventually.
I appreciate that singers have more difficulty here - impromptu lyrics can lead the lay astray!