I have done this now for six years. Sold five novels to UK publishers, but only one via an agent. My third literary agent is now trying to sell a book for me, but even at this stage there are lots of reasons why the book may not sell. I am currently publishing another book in a different genre myself, to avoid having to go through the process again.
It is nervewracking, but you do get used to it. The first time was awful and I was checking email every five minutes.