What does the scientific community know now that we did not know when you began the research?There is a similar probing question to ask yourself before you start a project (or a new sub-project). Suppose everything goes as well as can be hoped (i.e., you are able to complete the calculation, do the measurement, get the new technique to work, or make the compound). Then will you be able to say something new? If not, is it worth even trying?
The before question is a good one for both students and supervisors to contemplate. It is too easy for supervisors (including me) to say do this extra calculation (or make this extra compound and measure all its properties) without considering enough the time cost to the student or postdoc.