Why Do I Enjoy Being Beaten?

So, I have a few good posts coming up for you guys but I wanted to post quickly. I have had little to no sleep in the past 72 hours. Between not feeling well ( i know, shocker) and work...it has been a fun week. I worked from 8am-midnight last night and I put in about another 13 or 14 hours of work today. I have a huge client presentation due on Friday and with the changes that are being made it is taking me some time to get everything done. The thing is, as exhausted as I was, as much as my body has been pleading for sleep all day... I enjoyed it a bit.

I came home dragging from work, and carrying papers in my hand to finish some stuff I didn't need the computer for and decided to change and head straight to the gym. At the gym I pushed myself hard and beat myself up.

Why is it that I feel good after these things? Work is long and hard this week but this is when I feel the best. Working out and training for this half marathon has been long and hard but I feel GREAT when I come back from the gym.

It has made me think about what feelings are generated and why we feel good after these things. There are a whole myriad of explanations I have but I have to get back to work so I can finish and go to bed. Just wanted to jot down these thoughts before I forgot.