“Do not make riches, but usefulness, your first aim; and let your chief pride be that your daily occupation is in the line of progress and development; that your work, in whatever capacity it may be, is useful work, honestly conducted, and as such ennobling to your life.” – Andrew Carnegie, US industrialist.
This is good advice to bear in mind. Although ultimately your business will need to turn a profit, sometimes the value of the work you are doing can be measured in different terms to pure monetary value.
If you bring a product or service to market that will make life easier for everyone who uses it, you can take pride in the fact that your business is doing something of value for those people.
In the long-term this feeling will sustain you far longer than any short term financial boost.