Tell someone you’re vegetarian, and the first objection you’ll likely get is, “But where do you get your protein?” (Nevermind what kind of shape the person asking is often in.)
I personally have not let the protein issue affect me, choosing instead to cook and eat a wide variety of foods and trust that I’ll get enough protein and all of the essential amino acids, and I’ve never felt better. However, if you have any signs of protein deficiency, you should absolutely start making sure you’re getting enough protein in your diet.
For someone who cooks all the time, simply eating a variety of whole foods will likely get you the protein you need. But for someone whose schedule doesn’t allow for much cooking at home, getting enough protein from vegetarian foods (and the right kinds) can be a problem.
My mother is one such case. A few weeks after she became vegetarian, she noticed that something wasn’t right; she didn’t have the energy that she did when she ate meat. Suspecting that the problem was not enough protein, she spent a few weeks researching amino acids and protein in vegetarian foods.