I can concentrate much better after I've spent time running around outdoors, watching sunsets or listening to good music. I do not believe that the pleasure of being outside is more important than my other goals, but when I force myself to stay indoors and spend more time working I become too moody to concentrate and I get less work done in total than I would if I had 'wasted' more time. Cookies are different though, because the tedium of baking them outweighs the pleasure of eating them.