A lot of people assume that the key to happiness is learning to love yourself.  Those same people usually go on to say that you have to love yourself before you can love other people.  
Plenty of Christians assume that this is true.  There’s just one problem.  Jesus taught something very different.
He said that those who seek to save their life will lose it, but those who lose their life for his sake will find it.  (Matthew 16:25)  
And then, when someone asked Jesus to name the highest law, he gave us what we call the Summary of the Law.  Love God with all your heart, and soul, and mind.  And love your neighbor as yourself.  (Matthew 22:34-40)
He did not say, “Love yourself first, then love God, and then love other people.”  He said surrender yourself, love God, and love your neighbor.  
The reason he said this is that he understood who God is and what that means about human happiness.  In other words, Jesus was a good theologian.  And he calls us, his followers, to be good theologians, too.
This becomes especially clear on this Sunday, when our attentions are drawn to the most fundamental doctrine of Christian faith.  Today is Trinity Sunday.  
While theological doctrine may seem abstract and irrelevant to Christian living, I want to show you how knowing God as the Trinity transforms every day of your life.
To show you this, I’m going to address three questions.
First, why is doing theology so important for followers of Jesus Christ?
Next, what does the doctrine of the Trinity tell us about who God is personally?
Finally, how does belief in the Trinity lead to happiness in our daily lives?

Thinking about God
So, let’s look at the first question: Why is doing theology so important to followers of Jesus Christ? To answer this question, we need a working definition of theology.
Try this on for size.  Theology is the activity of trying to understand who God is.  Notice that I said “who,” not “what.”  
Natural science understands objects.  It measures mass and weight, atomic structure and chemical composition.  Natural scientists deal in causes and effects, mathematical formulae that describe motion, and laws that explain the phenomena that meet the eye.  This is the arena of questions that begin with “what.”
When we ask “who,” understanding means something else entirely.  Science studies objects.  Theology, by contrast, encounters a subject, a person.  Theology seeks to understand God on analogy with how we seek to understand a spouse, a friend, or one of our children.
Science requires that we stand at an objective distance.  Theology is always a part of overcoming the distance between God and us.  
When we do theology, we use our minds as part of a life devoted to building a relationship with God.  Theology is how we love God not only with our heart and our soul, but with our mind as well.  
When we understand who God is, we begin to understand his ways.  The better we understand his ways, the better we can follow them.  
The more familiar we are with his character, the more fully we can trust him to come through for us in a tough spot.  Our hope can be in the Lord no matter how we might happen to feel about things at the moment.
Theology is so important because it helps us to build a rich, deep, abiding relationship with God.  The foundation of Christian theology is the doctrine of the Trinity.  So let’s take a look at the groundwork of our faith.
One for All and All for One
What does the doctrine of the Trinity tell us about who God is personally? For starters, it explains that God is not a person.  He is three persons.  One being.  Three persons.  Father.  Son.  And Holy Spirit.
It’s paradoxical, I know.  But so is love, and we say correctly that God is love without apparent hesitation.  St. Augustine helps us to understand the Triune God with reference to love, so let me paraphrase him.
Love is three things at once: the one who loves, the beloved, and the activity of love that passes back and forth between the lover and the beloved.
The Father is the lover.  He loves the Son.  The Son is the beloved.  As the beloved he responds to the Father with love.  The Holy Spirit is the activity of loving that passes between the Father and the Son.  The Trinity is all for one and one for all.
Contrary to what many people think, the doctrine of the Trinity does not say that God appears to us in three ways or he has three modes of being or that he has three functions.  God is one community of three persons.
Before God ever created the world, he was reaching out beyond himself.  The Father loved the Son and the Son loved the Father.  
The Father does not dwell on the Father.  He loves the Son.  The Son knows himself first to be the beloved and then loves the Father.  
He does not busy himself with loving himself.  He doesn’t need to give love to himself.  Someone else has already done that for him.
We all exist precisely because God, by his very nature, is always reaching out beyond himself in love.  He created you and me and the whole universe so that we would enjoy being the beloved and reflect his love beyond ourselves.
Getting Over Yourself
Now we’ve come to our final question.  What does the doctrine of the Trinity mean for us? How does belief in the Trinity lead to happiness in our daily lives?
There is no question that we need to be loved.  That is why popular psychology teaches that we have to love ourselves before we can love other people.  Popular psychology is right about our need and misguided about what will satisfy our deepest longing.
The love we long for is unwavering and unconditional, infinite and eternal.  God created us finite with infinite longings.  In other words, he created us in his image.
We have all learned that other people cannot give us this kind of love.  Some of us have made the mistake of asking another person to love us enough to make our lives meaningful and happy.  And we discovered that the result was only a strained relationship and disappointment.
Some people then conclude that you have to love yourself.  But the truth is, we can’t love ourselves with the sort of love we yearn for.  We are finite.  Our love for ourselves can make us narcissistic, but it will not bring us tranquility and contentment.
I have heard Christians say that the Summary of the Law itself requires that we love ourselves.  They point to the commandment to love our neighbor as ourselves and insist that we love ourselves first.
But to love your neighbor as yourself does not mean that you have to love yourself first and then you love others like that.  
Instead, it teaches us to recognize ourselves as the beloved and then love others as God’s beloved, beloved just like us.  We love others because they are God’s beloved, and as God’s beloved, we delight in the one that God delights in.
In fact, the problem we all face is that we tend to love ourselves first.  That’s what it means to be a child of the fall.  We are terribly concerned about getting our due, securing our comfort, fulfilling our desires, and generally arranging our world according to our preferences.  
It is precisely our preoccupation with ourselves that leads to our greatest misery.  Jesus came to help us to get over ourselves.  And he is the very embodiment of the love—the only love—that can do this.  
God’s love is transforming.  God turns us into the beloved by giving us his love as a free gift.  He makes the unlovely into the beloved.
Believing in the doctrine of the Trinity helps us in our daily lives to get over ourselves.  That’s because believing in the Trinity is not just believing in a cluster of ideas.  
Believing in the Trinity means to rely on God for the love that makes life worth living and our neighbor worth loving.
This sermon was preached on Trinity Sunday, June 3, 2012, at St. Mark’s Cathedral, Shreveport, Louisiana.