Word of the month... Guay
Maybe you have heard this word before. If that is the case then we don't need to say that Guay expresses something good, that something is going well or that your conversational partner likes what you have said. Nowadays this word has a nuance that implies a mixture of naïveté, childish and comic. A child can say guay, but say it to an adult and it will sound almost like a joke—like when someone says córcholis when something goes wrong.
Knowing this, we'll tell you something few people know: guay wasn't always a positive expression. Even more, it has had meanings completely contrary to its present one. For example in the sentence: Tener muchos guayes (to have a lot of guayes) means to suffer from many maladies or bad breaks (as far as luck is concerned).
Over the years, guay has been used less and less as a negative term; although its usage as such is still acceptable. Of course, no one is going to tell you "He feels so guay that he had to go to the hospital"; but you never know. Just remember, when you hear this word, pay attention more to the context than to the word itself.