common sense

Once upon a time, i was 18 and i was a student.
My physics teacher taught us a good lesson : we have a brain and we need to use it so other people will not be tempted to think we are incredibly stupid.

As a valuable example, she told us that it might happen, even to the best of us, after long computations to find the temperature of an ice cube is 200 degres Celsius. In this case, and even if we are out of time, we should never forget to mention the above result is obviously wrong (*). Noticing this and stating it means that we made a mistake and we are aware of it. There is no shame in that, we are human and we all make mistakes ...
On the other hand, stating an absurd answer and not even realizing it leave the door open for other people to question our capabilities.
This was a great lesson, i might have forgotten everything about physics, but not this lesson.
I'll try not to forget it, and i will share it !

(*) i assume we all know that under "normal" pressure, at 200 degres Celsius, water is not ice nor liquid but a gas.