'Herein the disciple rouses his will to arouse wholesome states that have not yet arisen; and he makes effort, stirs up his energy, exerts his mind and strives.' - The Buddha
Simultaneously with the removal of the defilements (craving, ill-will, dullness/drowsiness, restlessness/worry, doubt). Right effort also has the task of cultivating wholesome states of mind. This involves two divisions: the arousing of wholesome states not yet arisen and the maturation of wholesome states already arisen.
Though the wholesome states to be developed can be grouped in various ways --- serenity and insight, the four foundations of mindfulness, the eight factors of the path, etc. --- the Buddha lays special stress on a set called the seven factors of enlightenment: mindfulness, investigation of phenomena, energy, rapture, tranquility, concentration (samadhi), and equanimity.
The seven states are grouped together as 'enlightenment factors' both because they lead to enlightenment and because they constitute enlightenment. In the preliminary stages of the path they prepare the way for the great realization; in the end they remain as its components. The experience of enlightenment, perfect and complete understanding, is just these seven components working in unison to break all shackles and bring final release from sorrow.
The way to enlightenment starts with mindfulness. Mindfulness clears the ground for insight into the nature of things by bringing to light phenomena in the now, the present moment, stripped of all subjective commentary, interpretations, and projections.
Then, when mindfulness has brought the bare phenomena into focus, the factor of investigation steps in to search out their characteristics, conditions, and consequences. Whereas mindfulness is basically receptive, investigation is an active factor which unflinchingly probes, analyzes, and dissects phenomena to uncover their fundamental structures.
The work of investigation requires energy, the third factor of enlightenment, which mounts in three stages. The first inceptive energy, shakes off lethargy and arouses intitial enthusiasm. As the work of contemplation advances, energy gathers momentum and enters the second stage, perseverance, wherein it propels the practise without slackening. Finally, at the peak, energy reaches the third stage, invincibility, where it drives contemplation forward leaving the hindrances powerless to stop it.
As energy increases, the fourth factor of enlightenment is quickened. This is rapture, a pleasurable interest in the object. Rapture gradually builds up, ascending to ecstatic heights: waves of bliss run through the body, the mind glows with joy, fervor and confidence intensify. But these experiences, as encouraging as they are, still contain a flaw: they create an excitation verging on restlessness.
With further practice, however, rapture subsides and a tone of quietness sets in signalling the rise of the fifth factor, tranquility. Rapture remains present, but it is now subdued, and the work of contemplation proceeds with self-possessed serenity.
Tranquility brings to ripeness samadhi (concentration), the sixth factor, one-pointed unification of mind. Then, with the deepening of samadhi, the last enlightenment factor comes into dominance.
This is equanimity, inward poise and balance free from the two defects of excitement and inertia. When dullness prevails, energy must be aroused; when excitement prevails, it is necessary to exercise restraint. But when both these defects have been vanquished the practice can unfold evenly without need for concern. The mind of equanimity is compared to the driver of a chariot when the horses are moving at a steady pace: he neither has to urge them forward nor hold them back, but can just sit comfortably and watch the scenery go by. Equanimity has the same "on-looking" quality.
When the other factors are balanced the mind remains poised watching the play of phenomena.
Maintain Arisen Wholesom States
Herein the disciple rouses his will to maintain the wholesome things that have already arisen, and not to allow them to disappear, but to bring them to growth, to maturity, and to the full perfection of development; and he makes effort, stirs up his energy, exerts his mind and strives. - The Buddha
This last of the four right efforts aims at maintaining the arisen wholesome factors and bringing them to maturity. Called the "endeavour to maintain", it is explained as the effort to "keep firmly in mind a favorable object of concentration that has arisen." The work of guarding the object causes the seven enlightenment factors to gain stability and gradually increase in strength until they issue in the liberating realization. This marks the culmination of right effort, the goal in which the countless individual acts of exertion finally reach fulfilment. "
By Bhikkhu Bodhi (Excerpt from the book, The Noble eightfold path: the way to the end of suffering)