One thing I have learned since starting my PhD is not to hold on to preconceptions. Of course we all work based on an idea of what the world is like. But as a scientist, you have to be ready to relinquish your theories in the blink of an eye if evidence shows otherwise. While in some professions, one can maybe get away without, it’s a lesson one learns by necessity when working in research.
There was a time during my PhD when my convictions about the problem I was working on got overturned about twice daily. All these radical changes in my ideas were kind of hard on me then, but I got used to this. It seems that even in everyday life, I now accept it much more easily if things turn out to be different from what I thought. I seem to be less disappointed.
I am not saying here that one should not have any ideas or assumptions, or call it theories, about the world. What I mean is that one should be able to let go of them without regrets the second they don’t fit anymore with new knowledge we have acquired.
Another important trait of a scientist is to be open to new ideas and solutions. Any ideas. Many problems were solved in ways that at first seemed very unconventional and maybe strange. By only sticking with what has worked in the past, one might miss important clues.
Some friends of mine take advantage of this, telling me some incredible stories and then laughing at me when I hesitate instead of immediately rejecting it as a lie. My brain somehow got used to admitting any idea to a thorough check (obviously I usually figure out after a few seconds that it was a hoax).
Looks like some aspects of the scientific open mind can also have their pitfalls in daily life ;-).