The Zen Entrepreneur explains why it is more difficult for bootstrapped entrepreneurs to focus on a particular market. I completely agree with the Zen Master on this one. It is more than necessary to keep the cash flow positive, because it’s way too easy to drown. As a result the lifestyle of everybody related to the company changes, and for the founder, the results are even more drastic.
In a funded company you can get paid decently well, but in a bootstrapped environment, the probability of drowning is inversly proportional to the square root of the money invested.
Do read the article if you are just started out, for it will introduce you to one of the most basic problems. Though as you go on, you will only find higher hills to climb.