Q&A Can You Further Explain Compartmentalization?

In dealing with the revelations of what has occurred during my husband’s affair, I struggle immensely with the subject of compartmentalization. My husband took my teen daughter to breakfast on their way home from visiting family. She discovered the affair before I did, and at this point was eavesdropping as my husband sent texts to me. Our text conversation can be summed up as this: he told me good morning, I can’t wait to see you, please send me a picture of your beautiful face, I can’t wait to hold you, and on and on. He had been with the affair partner all night about 7 hours earlier. At the SAME time he was texting me, he was having almost an identical text conversation with the AP. Beyond the obvious anger and disgust I felt when this was discovered (and dealing with my daughter’s trauma), I also feel like this takes lying and manipulation to another planet. Here’s the kicker: I think he meant what he said to me. I could list numerous other examples where he was a caring and loving person while simultaneously being the opposite. I think us betrayed spouses struggle to understand compartmentalization. Can you explain this mindset further?