I've been told not to use excuses, as per a "set of ethics", that if I gave reason for being late for an appointment, for work, not being a mathematician, etc. But, I don't see a moral difference between giving a reason for doing/ not doing something, and making excuses. If the justification I have is not extraordinary, or is not fabricated, how is it seen as less moral than another answer?
UPDATE, Feb. 26th, 2017: Since the Moderators can't decide if this is a question that is "off-topic" or not, I've tried to word it a little different than before, as per the Help Center Guidelines ~ Philosophy.Stackexchange.Com.
According to this excerpt from the same, there are places on this site where the question fits:
“Applied Philosophy — The more specific disciplines where philosophical methods are applied, such as logic and argumentation, the philosophy of language... social philosophy,etc."