Whenever we have negative thoughts, we try to stop them. We know they are not good for us and they drain us of energy, so we try to avoid them or change them. Because we are not always able to succeed in doing so, we begin to accept those kinds of thoughts as part of our lives.
I need to get into the habit of exercising my mind in order to keep it healthy. To exercise the mind means creating and stabilizing whatever consciousness is required at that time. That means if I need peace, I can hold on to that thought for however long I want to . This prepares me to deal with difficult times.