Bruises are a type of hematoma of tissue in which capillaries and sometimes venules are damaged by trauma, allowing blood to seep, hemorrhage, or extravasate into the surrounding interstitial tissues (reference). From what I read there seems to be two reasons why you notice a reduction in bruising.
The first would be because there is a deadening of nerve cells where they get used to the pain and eventually less sensitive. There could also be the development of some scar tissue from the bruising which has irregularly developed nerve endings leading to lesser stimulation. (reference 1 and reference 2)
The second reason could be because you yourself get stronger. The Wolff's law states that:
Bone in a healthy person or animal will adapt to the loads under which
it is placed.1 If loading on a particular bone increases, the bone
will remodel itself over time to become stronger to resist that sort
of loading.2 The internal architecture of the trabeculae undergoes
adaptive changes, followed by secondary changes to the external
cortical portion of the bone,3 perhaps becoming thicker as a result (reference).
So, repeated stress on the bones of your face/hands should be make them stronger. I don't think your body can adapt to heal faster in an area from repeated bruising as most likely scar tissue will develop from repeated stress on the skin. You can however improve your nutrition and diet to help your body heal better (reference).