“Think about what you are thinking about” is a popular piece of advice that is one of life’s most important.
Your thoughts can control your action, thus influencing your life. So, you have to ensure that you are thinking uplifting and positive thoughts at all times.
Sometimes, these destructive thoughts can slip into your mind, but you have to stop them in their tracks. The easiest way to do this is to displace them with positive thoughts.
Nature abhors a vacuum, so you have to replace the negative with positive. Do this every day and it becomes nature to you. It’s not easy, but also not impossible.