Exercise
Hi there! I do 35 minutes on the elliptical 4 days per week and I can honestly say I have NEVER gotten to that "euphoric" feeling after exercise! BUT, I can say that I definitely feel worse when I don't exercise. It will take a while for your body to get used to it, but once you do you will find that even though you may feel tired immediately after exercising, you won't need as much sleep, your endurance for everyday things goes up and you rest much better when you do sleep because your body can relax more.
Stick with it because it is so worth it. I was like you in that I started exercising long before surgery. I started because I was diagnosis with Type 2 Diabetes and it helped me to control my sugar numbers. But it did make it much easier to workout after surgery because I had already discovered that I rested better and felt better overall. I still don't like it. I don't do it for "fun", but I definitely feel like it is an important part of my life. I've discovered that I'm worth the time and the effort I have to put into my exercise program. Good luck to you, you are worth it too!