I hit my shin against the cross bar of my metal bicycle while dismounting. A strong sensation arose and I had to really focus to stay calm with the pain. At that moment, I asked my self, why am I recoiling rather than rejoicing? What has occurred that I register this as pain and wish these sensations to pass quickly?
What really is pain and pleasure and how do they differ? Pain seems to be what our being recognizes as harmful to us (if repeated). Clearly, there are different types of pain as well – emotional, physical, … Sometimes things that start out painful become pleasurable and vice versa.