To start with we need to determine what sort of person you are. We believe strongly that different things work for different people. For example we like to have structure and order in our life. We like to feel in control and having things organised into repeating patterns helps us feel more in control. Other people we know try to avoid structure. They don't like the repetitiveness and find themselves struggling to keep to a routine if one is ever imposed on them. Then there are those that like a bit of routine and structure for some things and are quite happy to let other things flow the way they do with little worry about routine. Basically what we're saying here is that routine effects everyone differently. Some people need it and some people don't.
Next we need to look at the benefits and pitfalls of each scenario. For example, in our case of liking structure we find that feeling in control reduces stress levels and makes us feel more secure with what's going on in our lives. On the other hand, if the routine is disrupted without warning or something doesn't go to plan it can adversely effect our stress levels. Similar things happen for people that prefer not to have the structure and routine - when things aren't structured they love it. But when a structure gets imposed upon them they can feel restricted and almost as if they're being controlled. Either pitfall with each scenario is related to stress levels.