Properly appreciated, therefore, the doctrine of the Trinity tells us what life is for. The doctrines of the Incarnation, Passion, and Resurrection of Christ tells us how God made it possible for us to attain the goal. For motivation's sake, it's always best to keep that big picture in view.
The homilist I heard yesterday, an old-fashioned Dominican who gives a six-minute homily week in and week out, made the distinction between knowing that God is a Trinity and knowing how God is a Trinity. Knowing the former is for this life, knowing the latter for the life to come.
That's a distinction that can be lost, to our detriment. We shouldn't treat the Trinity as a puzzle, but as our God. It is, after all, the Solemnity of the Most Holy Trinity, not the Solemnity of the Dogma of the Most Holy Trinity. We pray and worship the One God Who is Three, not the fact that the One God is Three.
And while "functional unitarianism" is a common enough phenomenon, it's not a difficult habit to break. In much the same way we learn to say "please" and "thank you," we can learn to think and to pray in a Trinitarian manner, simply by doing it.