Maybe one of the most important but neglected human emotions when it comes to design is boredom. Designers are always challenged by it. You do not want to design something that is boring. At the same time, what one day is exciting is the next day boring. What one day is designed in accordance with the most trendy and popular principles is the next seen as old-fashioned and boring.
To all those researchers who are trying to develop tools, methods, principles or theories aimed at supporting designers in their process, boredom is a significant enemy. What if you are successful in supporting and influencing designers to improve their designs in a specific way, you also with some certainty will make designs more similar and with that comes inevitable the sense of boring.
This is why anyone who is engaged in the challenged of improving design in any way or form, have to be very careful. The improvements, the influences, the support can not have any built in prescriptions of what kind of decisions, judgments, qualities, etc. are better than others, other than really foundational (or abstract) beliefs and values. These first intentions should only be aimed at guiding but not restricting the designer, to support reflection and opening up, but not limiting.
So, if more attention was payed to the notion of boredom, I think that todays theorizing around design would drastically improve.