"I just love my work!" How often do you really hear those words? Too many people just regard their work as "the boring and obligatory part of life", but it is possible to find happiness through work and stretching yourself.
We call it flow. Your work flows like a river, and you are flushed with it, and, what is the best, the world around fades out. There is only you and your work left. The great feeling of understanding the work thoroughly and knowing how it should be done gives you strength and persistence to carry on finishing the task.
I experience my personal flow in mathematics. It is easy to drown into the deep scientific dream once I have fallen in love with it. Mathematics gives me feelings of deep understanding and satisfaction when everything puzzling me suddenly clicks into place, and I am addicted to that bliss.
Flow is tailor-made for people who are capable of working intensively and not afraid of using their brains to find better solutions - flow is Mother Nature's prize to them.