What I write is completely comply with the statement, when you get knowledge you must have particular purposes behind getting knowledge about specific subject, for sure you have some goals in life. However, for an instance, your field is Biology but you want to become a Botanist then you study other things purposelessly even you don't take interest in what your field actually is, even if tomorrow is your exam and you are showing an irresponsible attitude and studying novels and other things I would say Its a waste.

When you mistrust someone and it is actually without aware of reality. You doubt on someone, and above all, you give a scarce punishment to the person. This fallacy of attitude should be avoided. Nevertheless, I named It "Doubt without fault"