Statistically, it should make no difference.
Sometimes you'll be giving away potential profit, sometimes potential loss.
But that's statistically - there is no advantage.
Reality is a whole other ballgame.
There is the inclination to chase losses, false "bravado" when hitting a winning patch.
Stress or panic resulting in deviation from the original plan.
If you're a rigid and disciplined punter, I'd say don't quit - there really is no advantage.
If any of the above applies, then definitely quit while ahead or down.
Tomorrow's another day
