I’m an author with one of the big five publishers in the U.K. and U.S. I know a lot of authors. I don’t know a single one without an agent.
I found the first draft of my first book quite easy to write. I didn’t put any pressure on myself. I aimed to simply write a book to see if I could do it; I thought of it as practise and I carved out time every day to write. I do find that when you start a book, you’re filled with energy and enthusiasm and can get a lot done but the pace, for me anyway, does slow and I get very bogged down around the 40,000 word mark - too far in to give up, too far from the end to see a light ahead!
For a first draft, the key is to just keep going to the end. When you have that done, editing is far easier. I really rate Stephen King’s On Writing which is very insightful into the writing process and full of useful advice. I don’t write in a similar style or genre to King at all but I still go back to this guide every time I write for a refresher and it’s invaluable. For advice on how to structure a really compelling plot, I’d thoroughly recommend Save The Cat! It helped me through my second novel when I suffered very much from the ‘difficult second novel’ curse.
Writing once I had a book deal actually became much harder. Then I knew that someone was definitely going to read it, I had deadlines and I had pressure. But the only way to write a book is one word at a time. You have to keep showing up and keep writing. Switch off the critical voice in your head that tells you it’s crap and just write. My mantra is always ‘I can fix it in the edit’. Often, the bits I think are the worst when I’m writing them are a lot better than I remember when I come back to them later.
Writing is a craft. It takes practise. Find a group of supportive writer buddies if you can - look for FB groups or on Twitter and find motivation and solidarity to keep going.
The more you read, the better a writer you will be. When I’m writing a novel, I prefer to read outside my genre so that I don’t constantly compare myself. Reading widely gives you an innate understanding of what works and what doesn’t.
Every writer suffers crises of confidence and thinks about throwing in the towel at various points in the writing process. First drafts are very hard but I promise it gets a lot easier once you’re through that stage. Good luck!