When it comes to selling books, something is wrong if you are not having fun. Very wrong.
Think about it. You have taken your book from an idea, to a manuscript, now to a published work. No one knows it inside and out like you do, and no one will be more passionate about sharing your message than you will.
Doing that should be fun, just like it's fun to show off your new car, your new baby, or your new home. I'm not talking about bragging and being obnoxious, but about genuinely being excited and passing along that enthusiasm. Remember, enthusiasm can be contagious, and nothing is better for a book than that kind of organic, grassroots excitement.
Not all phases will be fun, and there will likely be failures along the way. That's life, and nothing that is worth anything in life comes easy. Publishing a book is not for the weak at heart. You will face rejection, frustration, and trouble. That's par for the course and shouldn't discourage you. Resistance on the path to success makes you stronger, and as an author, a huge part of the process is finding out what works - and what doesn't - for you and your book. That takes time, and it is done by trial and error. But breaking through after hard work can be extremely rewarding.
Once you find what does work, replicate it to death. Have fun with it, be a blessing to others, and find a way to help people by using your book. Whether it is fund-raising, taking your children's book to schools and seeing the kids' faces light up, or challenging someone with exactly what they need from your book, these opportunities can be fun and provide a terrific outlet for spreading the word.
If doing this has become painful and is no longer fun, it's time to re-evaluate what you are pursuing. There are always new directions and possibilities to pursue.