Nightfall doesn't count as failure.But exessive nightfalls can happen and it is problematic. It can be stopped by doing this exercise. Works well for me. I do 200 times before sleep. I had "Nightfalls" twice in three days. Now, none. Understanding the effects of PMO on your body is an important part of the recovery process. This 40 chapter reboot manual by a successful Fapstronaut talks about all of this. Salvation HERE: https://forum.nofap.com/index.php?threads/6-years-clean-rebooting-as-the-best-remedy.135983/