When processing an image in Lightroom it is useful to check your work against the the original image you started out with. You an always revert back to your original image by going to the history panel on the left hand side of the develop module and selecting your original starting point titled “Import” which indicates the state of the image when it was first imported, then clicking back on the top most history entry to see the changes you have made. In my opinion this is just too much clicking to simply toggle between the “before” and “after” states.
Luckily Lightroom offers a little known keyboard shortcut to toggle between “before” and “after” and that keyboard shortcut is simply the “\” key. Try it you will be amazed at this simple time saving shortcut.