In terms of health, it's best to do any diet changes slowly over a number of weeks, by switching from say... ice cream to soy ice cream.. or yoghurt to soy yoghurt.. butter to nuttelex.
That's probably what I should have done I guess. I decided I was vegetarian and never ate meat again (I thought about it for ages first). Then after thinking about being vegan for a bit, I went vegan straight away as well. I didn't do the whole easing into it.
haha, I did exactly the same thing, but after talking to a few friends who work in nutrition etc. I'm told this is the best way to make any drastic changes to your diet.