A Night of Temptation

I've been with my partner for 25 years, and we were always so close. But last month, I felt this strange pull to someone else. We met up at a hotel just once. It was quick but intense, I remember his scent, the way he looked at me. How does something like that happen when you've been happy? I can't shake the feeling of betrayal and guilt. Am I going mad? Have any of you ever felt this way?