These three habits could be said to be arranged in a hierarchy according to thier strength. The same principal can apply to human learning. For example, in the Stroop test, reading is a stronger habit than color naming. If we call reading the Stroop test the correct response, the Stroop is a much easier task than if we call color naming the correct response. Thus easy tasks are those that are defined as having the dominant habit as the correct response.
Difficult tasks have a subordinant habit as the correct response.
When this happens the task becomes easy because the correct response is now dominant.