Forget it. You won't understand it. Your not suppose to.
Yup, it is frustrating especially when you are trying to think that we can "understand" God. We don't understand Him. We believe him.
He gives. We receive. He tells us who He is. We say, "ok." We can't even begin to understand that He (singular) is Three persons (plural). We say, "ok," we believe You.
Tri - three persons; une - one God. Geesh, it'll drive you crazy if you try to understand how Jesus died for you, but not the Father, nor the Spirit. It makes no sense, especially since there is One God. Whenever we try to explain it, rather than accept it, we end up thinking there are three gods, or we end up thinking there is one god who puts on three different outfits. Both are wrong and don't reflect what scripture teaches.
It is no different than believing your sins are forgiven. Jesus did the work a couple of thousand years ago, but at that point in time, he endured all the eternity of the punishment of God for everyone's sins. We say, "ok." We believe You, even though I wasn't alive when Jesus died for our sins.
Thankfully, God gives faith and strengthens it. He paid for your sins and the faith He gave receives the forgiveness Jesus earned. Then, the Holy Spirit is the person of the Trinity who strengthens and preserves you and the whole Christian Church in heaven and on earth.
"Ok, it doesn't make sense, but, "I believe... Thank you Lord."
Blessings in Christ,
prsell