"Fear is the path to the dark side. Fear leads to anger, anger leads to hate, hate leads to suffering." ~Master Yoda~
Be aware of your fears, face them with courage, for it is not that which you are afraid of that will destroy you, it is the fear itself that has that power. It isn't always the big fears that destroy our peace of mind, it is usually the little fears, called "worries" that bring us suffering.
What are you worried about? Being in the mindset of "what could go wrong" can work to your advantage if you allow it to push you to be prepared with a plan "B", or to take proactive steps to insure undesired outcomes are averted. In contrast, excessive worrying about things you have no control over will disturb your peace of mind.
Learn to distinguish between the two types of worries If you can take action to prevent an undesirable outcome, then be proactive or plan as you deem necessary. Then let the thoughts go, by reminding yourself that you have done what you can do and are prepared for whatever the future unfolds. If you have no control over what you may imagine happening, then there is no need to waste your mental energy upsetting yourself. Use whatever methods you find work for you to jump off of the worry train of thought. Being aware when you are caught up in worrying is one step closer to stopping it.
Worrying is a waste of mental energy and destroys peace of mind.
Begin to be aware of when your mind wanders onto worries. When you are worrying take appropriate action if possible to aleviate the worry. If the situation you are worried about is out of your control then jump off the worry train of thought. Take a slow deep breath and refocus your mind on being present or more uplifting trains of thought. The more you practice not worrying the less apt you will be to focus on things out of your control. All thoughts feed on attention. Don't feed worries and they go away.