Disclaimer: I don't own the show.
Booth and Bones were good at their jobs, catching the killer and analyzing evidence, but they had another hidden talent. They excelled at being undercover. Perhaps, it was easier for them to pretend to be someone else. Not having to think about feelings and work for just a little bit. Here they were at Brennan's high school reunion pretending to be a married couple.
They pulled all the punches to act like the other married couples: wearing the rings, talking like a married couple, and even dancing like a couple. The onlookers believed that they were a happily married couple. Little did they know, it was a great act of deception. After having expressed his desire for a relationship only the week previously, Booth didn't know how he was in the presence of her. He felt hurt by her excuse that she was protecting him from her. That she couldn't be the person he needed in his life. He loved her for who she was: the beautiful anthropologist who didn't understand pop culture and didn't believe in love and soulmates and yet had warmed her way into his heart without even trying.
As they danced, thoughts whirled in his brain. He was enjoying slow dancing with his partner more then he could say. The excuse of leaving room for the holy spirit was influenced by part catholic beliefs and his want to be in a relationship with Bones. He wanted to keep the distance so he wouldn't think about the two of them in 30, 40, or 50 years. He stated that night he would need to move on, but how would he move on after that confession. He brought himself to the present moment savoring the feel of Bones in his arms because he didn't know when this opportunity would present itself.