Sometimes routines can turn into obsessions. Or at least seem like one.
One of my routines is the morning coffee at the office. When I arrive at work I drop my bag at the desk and head to the kitchen for a cup of coffee. A simple routine, but the devil is in the details. Or in the cup in this case. I must have one particular kind of cup. If there aren't any of those kind clean I'll wash one. I can't drink from any other kind of cup.
Originally I chose the cup based on the fact that it's one of the most common kind of cup among all the cups at our office. It's also the same size and shape as the cups I usually use at home. It's effective and also familiar, safe. It's the same thing as with the shirt: I don't have to think about it. Another benefit is that it's easier to recognize my cup. Sometimes I move a lot arond the office and leave my cup in odd places. At least I can say it's not my cup if it's not that kind. Also if I have to wash one I usually also wash all the other dirty cups lying at the counter.
Routines can turn into obsessions and sometimes it might be hard to change. You do something because that's how you have always done. You are too used to it. But often there might be valid reasons for those obsessive looking routines.
In extreme cases, yes I can drink my morning coffee from other kind of cup. I won't let that ruin my day.