I share this because so many people think that when they are being positive, they shouldn't have one negative thought - ever. They should be nothing but positive and anything less is failing. This of course is absolute nonsense. Everyone, and I do mean everyone, gets negative thoughts from time to time. It is what you think most of the time that matters most. So just acknowledge any negative thoughts you may get. And replace them as quickly as you can with their complete opposite.
It's ok, and actually natural, to have negative thoughts. It is what you think most of the time that matters most.