If this is your first print run you don’t know what to expect. The book quality may not be as good as you imagined. It is safer to start with a couple hundred copies, then move to thousands later.
Another reason you shouldn’t print too many books is that you might be better off leaving the headache of publishing to publishers. Publishing yourself requires a lot of time and money. First you’ll need to learn about this industry, which will minimize your focus on the content of your book and reflect negatively upon your career.
Even if half of what you read is just for fun or doesn’t specifically apply to your art, you can still gain a lot of knowledge that will help you grow as a self-published artist.
Don’t get swamped in the world of social media. Interacting with fans is cool, and it raises your popularity, but remember that your time is limited. If you are running your own business then time is money.
Learn what’s happening in your industry. Maybe in few years time, manga will be more common as an e-book instead of an actual book. Be open to new ideas and experiment with new tools to attract more readers.
School, college and work may have nothing to do with art/writing, but it made you the person you are today. The experience you have gained from such stressful situations reshapes the way you think, behave and write. Enjoy those experiences and learn from them.
I’m glad I’ve taken every challenge as a learning experience and was able to see that throughout the past ten years, my passion for drawing and writing didn’t change at all.