Jacksterback - A mental trip you take while you're getting off. It could be

A mental trip you take while you're getting off. It could be from yesterday or from way back when you were still a baby.

I was jacking off and suddenly I was back in the bathroom at my grandma's house.

I had a flash of my first kiss while I was mid-slam.

I was getting off and I remembered when I got kicked out of the house.