Worry is like a rocking chair, it will give you something to do, but it won't get you anywhere.
We need to stop the rocking chair and just sit back and rest in God's presence.
When we relinquish our wills (thought life, attitudes, and actions) to our capable God, we are able to move past worry. I used to think that I had to muster up the energy and focus to quit worrying. To some extent, I am called to work, but God is the one that brings me the peace. When I turn my focus away from my circumstances and my desire to control, then I center my thoughts on my Maker, my Sustainer, my Healer, my Provider, and my Prince of Peace.
If you find your mind wandering back to that circumstance or person, submit your worry to God in a list. Write down a detailed list of everything that is plaguing your spirit and read it aloud to God (for your benefit, not His, of course) and then place the piece of paper in a box or burn it, if that symbolism helps you. Remember that our God sees everything, understands everything, and knows the future. He knows what is for our good. Romans 8:28