I was pretty much a vegetarian until I met my boyfriend. Being a true carnivore, he converted me over and I now eat beef somewhat regularly-- maybe once a week. I don't think it's good to eat too much meat, and there are some meats I will not touch (like pork), but a little bit of beef every once in a while can't hurt.
I also recently read an interesting tidbit in Mother Jones magazine by Kiera Butler about the fake-meat industry. That soy-burger you're chomping on may not be as eco-friendly as you think it is. Did you know that it actually takes more energy to process vegetarian meat alternatives (such as tofu, veggie burgers, fake sausage, faux hotdogs, etc) than it does to get some grass-fed steaks on the supermarket shelves? It's all the processing that they do to remove the fat from the soybean oil used in these veggie products. It's still better to eat non-processed whole vegetables, for your body and the environment, but it's something to think about the nest time you stroll down that veggie burger freezer aisle.