Lao Tzu has a wonderful observation about how our emotional state is tied to the place in time where we spend our mental energy.
He states that that people who struggle with anxiety spend a great deal of their mental energy in the future, whereas people who struggle with depression spend their time in the past. Finding ways to return to the present and focus on gratitude in the here and now can transform that anxiety or depression into peace and calm.
I use a simple centering exercise with clients which can help bring you back into the present. Perhaps this could help in bringing you back to the peace you're searching for.
You can do this exercise either standing or sitting, eyes open or eyes closed.
Start by taking a few deep breaths, using either your nose or mouth. Inhale for four seconds, hold for four seconds, and exhale for six seconds. Feel the air enter your lungs and your stomach, hold it there, and then release slowly. Focus on the counting and notice your body moving with your breath.
Now imagine a column of light inside yourself, starting from your heart, extending towards your head, and down through your torso. As you breathe, imagine the column of light extending past your head, and down through the soles of your feet.
Continue to breathe and imagine the column extending to the sky, and down through the ground. Feel the warmth and energy of being in the light. Spend as much time as you like inside the center.
When you feel ready to finish your time, imagine the light drawing back to you, and returning to your heart, from where it emerged.
Take two more deep breaths. Thank yourself for the time and carry on with your day.
Start with a few minutes at first, and grow your practice from there as you feel comfortable. What would your life look like with a bit more mental peace in it?