I think you should still be proud of your ebook. I released one of my ebooks five years ago that sold nothing for the first three months and even though it is old versions of software is still selling. The other thing is, your book could also pick up more momentum as you write more. One last thing, it's awesome that you actually wrote a book and didn't just publish a blank notebook that I see people doing and wanting to get rich from. Either way, appreciate your work.