The best way is always to stop when you are going good and when you know what will happen next. If you do that every day when you are writing a novel you will never be stuck. That is the most valuable thing I can tell you so try to remember it.
I believe in meditation - it's a good tool to centre yourself, but unfortunately, I'm too lazy to do it. It's very hard work, and I prefer to watch 'Nothing To Declare' on TV!