When is it best *not* to be curious or observant?

This weekend when talking about medical procedures, a witty niece shared this tip: Do NOT look at the instruments when you arrive :-) This makes sense. After all, why spook yourself more than necessary? This led to a question: When don't you want to/should be curious? An emerging Think, Try, Learn principle is that those two characteristics lead to a scientific version of being present. It's like my yoga teacher used to say: The past is over and the future hasn't happened yet, so the only living we have available is now. (They go on to say the body can only be in the present, so focusing on sensations will bring you here. I like the idea.)

Thoughts? Any good resources? How about Mindfulness by Ellen J. Langer?