In addition, the practice of virtue forces one to develop a number of the "concentration" factors in the sets themselves, on a preliminary level of skill, thus making them strong and fit for formal concentration practice. To maintain a precept, one must keep it constantly in mind: this strengthens mindfulness. One must stick to one's determination to abide by one's principles: this strengthens persistence. One must pay attention to the present moment , for that is where the decision to keep or break a precept is made; and one must remain firm in one's cultivation of the sublime attitudes : these factors strengthen concentration. One must be clear about one's motives for acting, and at the same time be sensitive in knowing how to apply a particular precept to one's present situation: ., being quick to see how to avoid an issue in which telling the truth might be harmful, yet without telling a lie. This strengthens one's ability to analyze the mind in the present moment, intensifying one's powers of discernment in general. These four factors — mindfulness, effort, concentration, and discernment — are the central elements in all of the seven sets. Thus, the practice of virtue exercises, on a rudimentary level, the qualities of mind needed for concentration practice.