It's a funny thing about the Trinity. Before you study any theology, it's a pretty confusing idea. After you study a little, you think you get it. But after you study a little more, you're confused again.
Without solid catechesis or serious study, the Trinity is hard to understand. He's three, He's one. How can that make any sense? A lot of preaching on the Trinity doesn't help much either. My experience of Trinity Sunday homilies is that they take something of this form: 'God is one, God is three, it's a mystery, please stand for the creed.' Too often mystery becomes an excuse for mystification. But that's another rant.
A lot of folks keep themselves from these troubles and cognitive dissonances by being functional unitarians, modalists, or Arians, often unknowingly. And it's usually not their fault; such departures from Christian orthodoxy are sometimes taught by our catechists and theology teachers. I've done it myself. As a volunteer religious education teacher I once gave some kids a lovely and catchy analogy for understanding the Trinity. Trouble was, it was very modalist in implication.
So, if you were in the multi-parish Confirmation prep program that met at St. Lawrence in West Haven, CT in the late 90s, where you had the young, cool teacher, and you now find that your prayer life is inexplicably confusing, or you find yourself in marriage preparation (the kids would be about the typical age now) with a priest with whom you seem to have theological differences that you can't put your finger on, feel free to blame me.
When you study a little theology you are delivered from all of this confusion, emerging into the clarity of claims about the self-diffusive nature of goodness, the necessity of the social Trinity, or the necessity of opposition and comparison for any distinction in being. You are comforted as your pious mind swims in the clear, living water of 'it's all about the overflowing nature of goodness' or 'it's all about the self-diffusion of love' or 'it's all about relationship, in a perfect communion of persons without coercion or domination' or 'it's all about the opposed relations which we imitate by the creative tension of human community life.' Your reflections wax sublime as you realize how original and mutual generativity structure the whole of both created and uncreated being, and so realize how happiness lies in making our own relationships and generativity imitate God himself.
But then you keep going, drilling deeper into the sources of these reflections and the theologians and other sources from which they have come. Cracks start to appear. You start to notice that each effort at a theological articulation of the great Mystery succeeds in taking some of the data of revelation and some of the orthodox confession of faith seriously, but not all of it. Each approach succeeds in avoiding modalism on one side and Arianism on the other, but you realize that this feat alone doesn't mean every problem and question has been resolved.
So you're back where you started, wondering and confused. But perhaps with a greater and more prayerful appreciation of the Mystery Himself. And maybe that's the point.