People have been asking this question for hundreds of years. Linguists have been paying special attention to it since the 1940's, when a linguist named Benjamin Lee Whorf studied Hopi, a Native American language spoken in northeastern Arizona. Based on his studies, Whorf claimed that speakers of Hopi and speakers of English see the world differently because of differences in their language.
What we have learned is that the answer to this question is complicated. To some extent, it's a chicken-and-egg question: Are you unable to think about things you don't have words for, or do you lack words for them because you don't think about them? Part of the problem is that there is more involved than just language and thought; there is also culture. Your culture—the traditions, lifestyle, habits, and so on that you pick up from the people you live and interact with—shapes the way you think, and also shapes the way you talk.