One thing that may help with your design process is to use the History and snapshot options. You can make a few changes to the design using the dodge and burn tools and if you don't like it, just click back a few steps in the History palette. Or you could take a snapshot at the time you like it most. Then make further edits and if you don't like them, go back to your snapshot. I have a tutorial available for further information at
Photoshop Tutorials - History Palette