After months of rising confidence, small business owners are not as optimistic, according the latest mood-gauging index.

The Discover Small Business Watch reported that its index, which measures economic confidence, fell to 86.1 in June from 87.4 in May. The drop in the index is thought to have been caused by business owners worrying over having access to enough capital to successfully run a business. The number of small business owners who said that they were having problems with funding rose to 51 percent, up from 45 percent in May. The number of small business owners who have been worried about access to cash has not been at that level since January.

Despite money worries, small businesses are looking forward to a brighter future. Thirty percent of those polled said that business conditions are improving, which is higher than the 28 percent who felt the same way in May. And according to Discover, it has a lot to do with hard work.

"Many small business owners are working harder than ever to make payroll, pay their bills and keep their businesses running," said Ryan Scully, director of Discover's business credit card.

Discover, which commissioned the index, reported positive news in recent days. Discover Financial Services posted a profit in the second quarter based on increased consumer spending and higher gas prices. The shares of the company's stock rose 2.9 percent the morning of the announcement, going up a total of 41 cents.