Getting traffic to your site is only half of the battle. You also need to keep people on the site, make conversions and make sales. This is why quality content, rather than keyword spamming, is so important. You need the type of site that not just ranks highly, but that offers information and that keeps people on the page.
Maybe you’ve been noticing that people are leaving your site more often than you’d like, and after far less time than you’d prefer. Many of them just land on the page for a second or two before closing it, indicating to you that it did not give them what they were looking for.