Do you know how many s c vegans binge on animal foods, secretly, and then try to forget about it and hope for a fresh start towards the perfect vegan lifestyle? I met so many vegans that also say they will sometimes eat dairy/eggs/fish etc, but not for health issues but because they are invited etc, and then call themselves vegan and say "look how healthy I am".
My experience is that most vegans cheat/make "mistakes" , sooner or later, and that they can keep on doing the vegan thing - just because they are "making exceptions" and the body gets just enough to keep on going...