I guess that I am going to go off on a different tangent with the Trinity. (Please note I do not mean to downplay the mystery, but I like examples.)
The Trinity is like an egg: it is shell, albumen and yolk. Each is the egg, but they are all the egg together. Imperfect example, but tangible.
Also, water. There is water, ice and water vapor. Each exists together and separately at the same time.
I like the story of St. Augustine walking on a beach thinking how he can explain the Trinity when he sees a boy running from the water to a hole in the sand. As he comes closer, he notices that the boy has a cup of some sort and is taking the water from the sea to the hole. He approaches the boy and ask him what he is doing. The boy tells St. Augustine that he is taking the water from the sea and filling the hole. When St. Augustine tells the boy that he is attempting the impossible, the boy answers, “It is like trying to understand the Trinity.” Then the boy disappears.
Hope that helps. That and the fact that Catholics embrace the idea that we are not necessarily supposed to (or for that matter, that we can) understand God.