Cheerfulness

My wife may have discovered something today. She made a chart for Sierra that consisted of jobs for her to do. If she did the job cheerfully she got a check-mark. She will, of course, receive some sort of reward, however what struck me was Sierra's cheerfulness. Are children that work more cheerful than those that do not work? I don't know that I am more cheerful because I work, all though when I work and see progress I also feel good about myself, thus I am probably more cheerful. When things go sour, I can be very morose. So, how does work relate to your outlook on life? By the way, we will see how cheerful Sierra is tommorow when she looks at her chart...