Research on the thinking processes of children have found that often they overestimate how well they are going to perform on tasks, because they imagine that they will work very hard to accomplish those tasks. This mental shortcut is known as

the effort heuristic

Explanation:

Effort heuristic: In psychology, the term "effort heuristic" is described as a "mental rule of thumb" whereby the worth or quality of a specific object is being determined from the discerned amount of efforts that generally went into creating that specific object. In other words, effort heuristic is referred to as the amount of an individual's efforts that he or she is willing to put into a specific action will depend on the goal.

In the question above, the given statement represents the effort heuristic.