Oft times I'll switch up my route to make it interesting. There's plenty to see. I also make it a habit of talking to people I see on the way. This makes it more of a interesting ride, and they also ask what happen when I'm not there ~ semi motivational.
It depends on how rough the ride is for you too. I, uh, named the hills on my various routes, and sometimes mid day I'll pick one to "killl". Just don't talk about it out loud. I have a hill I call "The church" because it has 3 churches on it. One day I said out loud "I think I'll kill the church today". That got some WIDE eyes.