Why does everything hurt?

This is the second day of my new INSANITY workout regime and my body still hates me. Well obviously, after roughly six years of light living, it wouldn't respond favorably. It has been quite sometime since I have had my ass kicked like that. It's been a very sore day and will continue to be that way.but its a good kind of pain and hurt. The kind that reminds you that you've actually accomplished something. It feels great to be productive, to actually be doing something. It's something that I now realize that I have been missing. While it may take awhile to get where I eventually want to be, it will be well worth the effort. Once again, it is time to release the beast within.