Once you have the training its actually easier than doing things like being a clerk at Walmart. Jeff is right, its not easy. You will have to work your brain and your muscles. But compared to a lot of jobs that will be boring and miserable it is easy.
Most of us love science BECAUSE it’s hard–it’s a challenge–and we love the thrill of the chase! Whenever I think it might be nice to do something that doesn’t require quite as much thought, I remember just how boring that is, which actually makes it harder for me to get motivated to work.