Saying that creates fear. Who does not fear suffering? How is concern about possible futility not discouraging?
People who say they cannot accomplish anything meaningful in only half an hour, do not say this out of laziness or the lack of a practical sense, but because they have not gained confidence or have had it destroyed.
You have to say it is going to be relatively easily, interesting and perhaps enjoyable, and feasible. You have to feel you may possibly make actual progress. It is not useful to go on to people about how hard things will be.