Challenge will teach you new skills. It will motivate you to get the best possible performance from yourself. And on days when you don't have much you have to do, you don't get much done. Just as your effort increases to meet the job that must be done, so too do you grow enough to meet the challenges that come our way. To become the person you want to be, you simply find the challenges that will take you there.
Any worthwhile achievement is largely a matter of meeting one challenge after another.