Reality
You can never stop having dreams, but can you ever achieve them? Being a realist is looking at the big picture and saying "what do I need to do to get there?" Dreams are sometimes like fairytales. They seem real to a certain point, but there will always be the aspect of 'this isn't real and it can never happen'.
Being a realist can be a "buzzkill" because you come up with dreams, then you shoot them down because you know in the back of your mind that it's never going to happen.
Things like owning a cat can be real, but if you're allergic to them it's not because in some way you're risking your life. Things like becoming famous can't be a reality if you don't have a plan or a great idea to show the public. Realistically, if the chance is 1/million, it's probably never going to happen. If it's more like 1/10, then it's more likely. Being practical and being a daydreamer is different. It doesn't mean you can't be both, but it's best if you changed your views so you don't discourage yourself from doing something great our something that 'could've been'.
There's a fine line between chasing your dreams and shooting them down.