Because of risk, in the case of consent it should be a binary. Yes and then no, means no. Open communication about what both parties want to do is key, sometimes exploration is part of discovering that, but first there must be explicit consent that both partners want to try something. Realization that it is not something wanted, does not grey the earlier yes, nor does the earlier yes have effect on the current no. The learning&respecting process is part of healthy relationships/scoodilypooping.