A student of mine recently sent me this video. Find out what riding a bike and learning a foreign language have in common: https://www.youtube.com/watch?v=MFzDaBzBlL0&feature=youtu.be
We English speakers often have the mistaken notion that a) we're just not gifted in the area of foreign language, or b) we'll just check that off our list in high school and be done with it. The best time is to start children when they're young.
But don't let that discourage you from starting NOW, no matter how many years you've been on the planet! (Click here for some encouragement!)