Is it impossible to become good at a martial art if you didn't start at, like, 6?

I use to practice Tai Kwon Do, when i was like 10. I did it for about 2 years, but ended up quitting. I'm now 16, and ma considering taking up Taijutsu. Is completely impossible for me ever to become good at it? I hear u gotta start these thinsg when ur really young.