I am Polish and I have this sign hanging on my fridge to remind me of these simple yet powerful words "Be at Peace." In a world that is suffering and always needing to "de-stress," peace is something that is very much sought after. It is hard when we feel like "our world" is falling apart around us and there seems to be no answers to our problems, but Our Lord said, "I have overcome the world."
St. Therese talks about suffering from moment to moment, which was the only thing that brought her peace. True peace comes from God. I know when things are upside down in my life, it's those quiet moments before the Blessed Sacrament that bring peace to my heart. Our Lord said again, "Come to Me all you who labor and find life burdensome and I will give you rest." Rest is that peace that He alone can give.
Acceptance helps us be at peace as well. There may be things we simply cannot change that are overwhelmingly challenging in our lives. We may have to accept them without understanding. It is then that we must look to Christ Crucified which is the only place that suffering makes any sense.
I love this quote of St. Francis de Sales: “Have no fear for what tomorrow may bring, the same loving God who cares for you today will take care of you tomorrow and every day. He will either shield you from suffering or give you unfailing strength to bear it. Be at peace, then, and put aside all anxious thoughts and imaginations.”