"Nothing is easy to the unwilling." Thomas Fuller, 17th century British historian
Oh, dear! How very "shame on you!" this sounds. Like an admonishment given by a teacher to a student who, the teacher is convinced, is only failing because of laziness.
This is not to say that the statement itself doesn't hold a grain of truth. However, it does not follow that everything comes easily to the willing. For example, how many people in the USA are currently unemployed, not because of willingness to work but because of a shortage of jobs?
Rather than encouragement, this quote resounds with judgement. I find its presence on an "uplifting" calendar quite objectionable.