Thought are things. Thoughts are your reality. If your thoughts are negative thoughts, those thoughts will and do come true.
To change the subconscious patterns of our mind, we must explain away old habits and patterns. For Example, if you have fear of success, you will not take enough responsibility for daily things to succeed and therefore NEVER reach success.
This process takes time and constant awareness. Just like anything else, you cannot fix what you don’t know is a problem. Recognize the negative thinking, then you can work on changing that to positive thoughts.