Sunday was Trinity Sunday and the homilist was expounding at length on the difficulty in understanding the Trinity. This concept still is a hard one to understand, despite having been pondered by the greatest minds in Christendom for almost two millennia. Some Christians, such as the Arians and Monophysits of old times and Unitarians of today, gave up trying to understand it and found it unworkable.
I remember my mother teaching my first grade CCD class trying to explain it to a bunch of six year olds. Needless to say, we did not quite get it. I remember was my mother finally saying "think of it is you, your mother and your father tried to bake some cookies together" - so I think she ran out of ideas also.
But my favorite story is that of Saint Augustine, walking along the shore of Hippo, pondering the problem of the Trinity. There he saw a young child dig a hole in the sand. She then began taking buckets of water from the Mediterranean and started pouring it into the hole. When Saint Augustine asked the child what she was doing, she replied that she was trying to puring the sea into the hole. When Augustine told her that was impossible, she replied that she would pour the entire sea into the hole before Augustine was able to understand the Holy Trinity.