Writing is a lonely enterprise. You can spend months or years creating a novel, all the while with no assurance it will interest an agent or publisher at all.
Joining a group—a local, regional, or national organization of writers—can not only alleviate the loneliness, but it can also offer training and tips, provide invaluable advice about the business from those who've climbed further up the literary mountain, and open up opportunities for promotion.
For years I've happily belonged to Mystery Writers of America (MWA) and a Southeast sub-chapter (SEMWA), and to International Thriller Writers (ITW). These organizations offer fellowship (if that word is still politically correct), valuable business contacts, and excellent advice on every aspect of writing and publishing. I've learned much just from their newsletters, which I keep on file for reference. Both organizations publish excellent short story anthologies open to member submissions. Both are heavily involved in conferencing functions. I've recently joined the North Carolina Writers Network, as well. They sponsor two conferences and respected writing contests of their own each year.
There are many unexpected benefits. For example, I served three years as an ITW awards judge, twice for novels and once for short stories. I had to critically read a wide array of authors from all over the world, authors I never would have been exposed to otherwise, and that couldn't help but broaden and enhance my view of the craft, and to teach me a good deal. Plus all those books I got to read were free.
There are a goodly number of similar organizations from which to choose. Sisters in Crime (bit sexist, that, but they do accept a male or two), Romance Writers of America, Western Writers, the Historical Novel Society, Science Fiction and Fantasy Writers of America, even the Cat Writers Association, whose members write about felines.
Any of these fine organizations will warmly accept like-minded souls who are struggling to achieve success. So fill out an application or two. Learn the secret handshakes and online passwords. Banish that loneliness.