It's possible for *some* people. Not all, not most, and not really *many*. There's a large portion of the populace that once they cross a line, such as being intimate, it's difficult to completely put that back into the bottle and never cross that line (or come close to crossing it) again.
It can also add a lot of stress to a new relationship if the new person isn't 100% secure. (Which is extremely common with many many many many people as we all know.)
"Well, then," the Cat went on, "you see a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."