I'm taking Chinese this semester. It's difficult for a guy my age (43) but it also a lot of fun. Practice practice practice.
I'll be going back to school next fall (I'm 28) and will have to complete the foreign language requirement. I took two or three semesters of Latin my first time in college, but it's been so many years that I can't just start where I left off. I've been thinking about starting over in another language, maybe Chinese or Russian.
I studied it (college level) when I was in my early 50s - 20 years ago. One of the best things I've ever done. It is an absolutely fascinating language. I'll never be fluent (don't get enough practice) but it is with me constantly. I do something with it, in some way, every day.