Learning a new language transforms your brain for the better. The process creates new connections between your neurons; brains with more connections perform cognitive functions better than those with fewer connections. More connections between neurons means more electrochemical firing between these specialized brain cells. In essence, you become smarter. You retain information with greater ease and accuracy. You increase your ability to communicate, imagine, problem-solve and create. Learning a new language trains your brain to better interpret information from any language.
Read one or two of the thousands of books that have yet to be translated into English. You can read popular fiction, academic and scientific journals and scriptural texts of religions such as Taoism, Buddhism and Gnostic Christianity. You can also appreciate translated works in their original language. Gain literary insights by reading the Koran in classical Arabic or the poems of Pablo Neruda in the original Spanish.
Language both constructs and limits thought. Different languages give you access to different worldviews, expanding the kinds of thoughts one can have. In the Yourba language, there are no gender-specific pronouns. Instead of "he" and "she," there's a single third-person pronoun covering both of the sexes. In French, Spanish and numerous other romance languages, adjectives come after the nouns they describe ("car red" rather than "red car"). The Japanese system of grouping words is not based on tens. Thinking in a non-native language gives your brain a chance to conceptualize the world differently.
Learning a language gives you confidence when travelling abroad. For long trips in another country, learning even a few conversational phrases can go a long way toward increasing your quality of life. You'll be able to get home by taxi without having to drive all across town. You'll know how to ask for the location of the produce you want at the grocery store. Even if your accent is terrible, you will gain positive attention for trying and native speakers will help you get better.