As you likely know, all images are different and bring different attributes to the table. Because of this, not every action will appear the same on every image. Some actions will appear too subtle for certain image conditions, others will appear to harsh. No worries, this can be easily manipulated in Photoshop! Actions can be tweaked and blended to achieve your desired look for ANY photo! Here I will discuss the two primary ways actions are typically modified: 

The tried and true method for quickly adjusting an action, involves adjusting the opacity (or "strength") of the action's effect in your Layers Panel:

Another, slightly more complicated method, involves those actions that are grouped. These will typically be your actions which change more than one setting, those global toning actions which change the overall look of your image across several steps. These actions can be further manipulated on a layer-by-layer basis within their groups:

You can also selectively modify parts of your image utilizing the white mask present on each action with a soft black paint brush. With the white mask selected on the feature you want to manually shape, simply paint the areas you wish to remain unaffected by the action: