Does Breaking the Routine Pay Off?

Unlike every other day this year, I changed my routine a little yesterday to try to achieve a distance goal for the end of the year. In my case, I added 20 percent to my distance. Wow, what a difference it made to my feeling of accomplishment, endorphin kick (it lasted all day long), and just plain physical feeling (pumped up). Generally one day has been the same as all the rest. This change really made me feel better. I'm a routine oriented person which is probably why I can swim laps day in and day out. I've worried about changing my routine because I've not wanted to create a reason to not workout. This small change which added about 15 minutes to my workout seems to have made a big change in my attitude. I'm wondering if other alterations may do the same?