One way to use this in marketing is to get someone to make an easy decision, and then get them to take actions on their own so that they can prove to themselves that they made the right decision. People usually want to validate that they made the right choice. Another way to work this is to give them that validation early on so that when it came to the sale, they will have already eliminated their dissonance and they will buy to reinforce their belief. In a happy room, most people get happy. In a sad room, most people get sad.
People conform to the emotions of the group or environment.
That is why casinos and top retail outlets try so hard to create an emotional atmosphere of carefree spending or something similar that will cause emotions that lead to spending. Have a look at your site. What emotion does it convey. A site's text, prose, colors, graphics and quality can make or break an online business just from the emotional angle. Same thing with banners and other ads that you do.