When I was in Bible school, one of my classes was a survey of the New Testament. It was an elderly British pastor who was trying to teach us the theology of the Trinity. It almost went like “Okay, there's Father, Son, Holy Spirit. They're three; they're one; they're like a shamrock; they're like a light bulb.” Most of what I walked away with that day was "God's like a…shamrock? I don't know if that makes me want to worship him.”
A similar confusion and ambivalence about the Trinity seems to hang over the church today. A common understanding of the Trinity is that they’re three persons. Somehow they're also one, but we don't know how. We don't really want to explore that too much in depth either, so there's this disconnect from who God really is.
In my early days, when I would read John where Jesus said, “The Father and I are one,” I would think, “Wow, they're really close. They're good friends. They're really intimate.” However, that’s not necessarily understanding Jesus, the Father and the Holy Spirit’s relationship. It’s not a friendship or relationship in the sense that I'm one with my wife. Jesus was talking about essence and substance.
Understanding this — truly getting it — is so important! If you just saw Jesus as sort of an independent figure but not a complete part of the Godhead, he wouldn't have the power to save because he's not God. At that point, he's just a good teacher. If we've never sat down and studied the doctrine of the Trinity, we're going to run across it in scripture and think something along the lines of "Okay, the Father did this thing in my life, and then the Holy Spirit separately did this other thing."
If you deny them as Trinity, though, you're going to find yourself falling short. You can't really know God or anything really deep about him unless you see him beginning to reveal himself in this form of three persons and one essence.
We have to dig deeper, take more time, be more patient, maybe a little more humble. We have to understand that we really don't know God like we think we know him. As we truly seek him, though, our entire walk with him will transform.