One of the nice things about Lightroom is that it lets you view before and after versions of your image. Lightroom can do this so easily because it does not make permanent changes to your image as you work on it. Instead, Lightroom keeps a log of the edits that you have made and only applies them to the image when you export the image. Use the Before/After options in Lightroom to check that the changes you have made to your image to make sure that you’re headed in the right direction.

Lightroom: Controlling the Before and After