What Actually Happened

My son almost drowned in the swimming pool at a hotel we were visiting. I didn't see him. I cannot believe that I didn't see him. Of course, neither did the lifeguard -- things can happen so fast. When I saw him he had pulled himself out and was sitting there dazed. I called for him and he staggered to me. I was so scared and felt so stupid. But he is okay. It is God sustaining him.
But I keep thinking about it. I keep thinking, What if he hadn't pulled himself out? What if I hadn't seen him at all? Why wasn't I swimming with him like I usually do?
Over and over.
We were laying in bed after this incident and Eric asks me -- What are you thinking? When I told him I was thinking about Zac, he wanted to know what I was thinking about him. It seemed pretty obvious. My son could have died and it would have been all my fault.
Then he challenged me with the words from Philippians 4:8. "Whatever is true...whatever is right...think about these things." The point is that he didn't die. Why do I keep beating myself with "ifs" that didn't even happen? Why do I keep focusing on myself and my failures instead of thinking about how glad I am that God spared him? Why pretend I can change the past? Why do I want to imagine it was worse than it was? And then, why do I let it haunt me?