This is an addendum to my previous post: Just like the stuff you write is text, not you or your soul or your baby or whatever other metaphor people use to indicate that they have overidentified with their writing, your business is not you, your soul, or your baby. It is a financial investment.
More specifically, it is a long-term, high-risk investment with poor liquidity. There is certainly a place for something like that in your portfolio, but you should NEVER have 100% of your money in a long-term, high-risk investment with poor liquidity.
People say "I plowed every last dime back into my business!" as though this were a marker of great virtue, when the fact of the matter is, from a personal-finance perspective, that is no different from saying, "I plowed every last dime into my collection of antique cars!"
It can be difficult-to-impossible to find a buyer for any business. And writers in particular have traditionally gotten screwed when they sell their rights. If your business is making money, you need to 1. pay yourself, and 2. use that money to diversify your finances the hell out of that business. If that leaves you with less to spend on your business, that's fine--a little spending discipline never hurt anyone.