Many meat-lovers who know deep down that it is better to be vegetarians are nevertheless fixated on the idea that one is either a full-time vegetarian or not. The truth is, it need not be so clear-cut. If one truly realises it is better to go vegetarian, but is still attached to the taste of meat, one can still make a point to be vegetarian most of the time, or choose to eat less (and less) meat.

Just because one chooses not to commit to being a full-time vegetarian doesn't mean there is no way to be an “almost” full-time vegetarian. The same logic would apply to the vegan cause. Whether one is already a vegetarian or not, if one sees the advantages of being vegan, one should strive to be vegan as much as possible; instead of not trying at all.

To be true to one's understanding of the benefits (to one's health, animals' welfare, starving humans, the planet's health...) of vegetarianism is to try one's best; to not excuse yourself totally just because of greed (or any other reason) for meat. Of course, even if one is vegetarian most of the time, one should not “undo” one's efforts by feasting on many animal products occasionally in one go. That too, would be being untrue to the vegetarian or vegan cause.

Irrefutable Rationale to go Vegetarian:
http://www.viva.org.uk/goingveggie
Irrefutable Rationale to go Vegan:
http://www.viva.org.uk/goingvegan