Today is a very somber day. It's a day we stop and remember the passion of our Christ. Can you imagine the way he felt. Betrayed by one of his loyal disciples, stoned, mocked, and humiliated. This is the chosen one who came to Earth to save us. What did he do, continued to love and said "Forgive them they know not what they do".
Today many Catholics Christians start the Divine Mercy Novena. It's especially close to my heart. As a convert, this was all foreign to me and I had many.... many questions about "catholic" devotions.
The main verse repeated is "For the sake of the sorrowful passion have mercy on us and on the whole world".
It's just a beautiful prayer. Take a moment look over it and if you don't feel called to say the exact wordings just think upon the passion and ask for mercy. Here is an online explanation.
This prayer is to be said at the 3 o'clock hour. It's the time they estimate that Jesus passed.