Why do I develop bronchitis so easily?

I just had severe bronchitis during the Thanksgiving holiday. It takes me a while to get over bronchitis. I was finally over it for a while. Now I have it again in January just two months later. Also, every time I get bronchitis, I don't just get it a little. I always get it really bad. Why am I getting bronchitis so much? Is there something I can do to prevent myself from getting it so much?