It’s an aspect of post-nut clarity. When I started this hobby and had my very first finish, I was like, “lol what am I doing here seeing an SP I could’ve done this at home” as she was getting the towel to clean me up.
For us without SO, the guilt may come from spending too much or partaking despite being against one’s religion/values.
Still, I usually take longer sessions for MSOG, feel guilty again, go home, then 2 days later browse terb/twitter cause I’m a horny boi.