@Aleksander - I'm going to guess from your name that you are of Eastern European descent. I know from experience that culture really can't imagine being healthy without eating meat. My Polish grandmother was terrified that I would get sick from lack of meat (actually, I think she was convinced that I would die *immediately* lol!)
The key is to be a real vegetarian, not a junk food vegetarian. I knew several people in college who called themselves vegatarians who lived on a steady diet of Doritos, pizza and white bagels.
Eat real food that comes from plants as the basis of your diet. Stick to whole grains and if you're going to eat cheese & eggs, find quality sources that are free of hormones and antibiotics. Variety is your friend. If you do that, you'll be just fine.