Hi Mary,
Glad you found my post interesting. To answer your question. It is presumed that we all know good from bad, including thoughts. So what you have to do is Stop, and think about each (wanted/unwanted) thought, and ask yourself, do I want to KEEP this or NOT. If yes, then let it into your mind. If not, then cast it out and think about something positive to replace your bad thought.
Mary, this is a really basic explanation. If you want the name of the book let me know.
