With a whole slew of vegans becoming ex there are some very clear common traits on how to make a mess of a vegan diet. Gojiman makes a good summary of this
youtube.com/watch?v=JwVkcjl...
The takeway point, no-one fails on a vegan diet if they regularly eat a varied whole food plant based diet. By the word varied I mean nuts, seeds, veg, fruit, legumes most days.