If you complete 9 out of 10 tasks successfully, your senior ignores 9 tasks which are done.

In a Managerial Position everything is important.  A Boss cannot ignore even 1%., Perfection is possible only with 100%

I agree with Mr. Venkit ... Though he should consider the9 tasks done... But, if that1 task is crucial & are interlinked with other9 tasks ... & in business your boss too responsible for your actions thus nothing can be left behind... Tasks is considered complete only when it is done100% .... . :-)