"...I really want to do CPR on someone..."

You have to keep in mind that, depending on the circumstances, you might not be able to save the victim. Then you have to live with that. Some people have a real hard time with that. Luckily (I guess), I am not one of those. And you can get real tired if you have to do it long enough. I have done full blown CPR, all by myself, for over 30 minutes in the past, and I was really tuckered...