Misery enjoys company. Every time.
A writers group is kind of like going to rehab, only with much lower expectations of "recovery". Make no mistake, if someone has suggested that you join, (that person is not your friend) or if you have somehow arrived at the depressing conclusion that you NEED to join a writers group, it's already too late.
Writing is by nature, a solitary exercise. It's really just you and your talent, taking on all comers. The minute you admit that it's not just you and your talent, the fight is lost. You're now just another hack waiting to be pounded senseless.
If being in a writers group hasn't already convinced you that being an aspiring novelist is futile, open the pdf.