The Seven Factors of Enlightenment Are the Seven Factors of Enlightenment understood to happen as specific phases in a linear progression in one's journey or are they understood to happen in a circular manner with ever deepening understanding?
I like to teach them as linear, but it's not really that simple. The Buddha said (SN 46.53) that when the mind is agitated you should cultivate the last three (tranquility, concentration and equanimity), and when the mind is sluggish, the second through fourth(investigation of dhammas, effort and rapture):

&quot;At such times, monks, as the mind is sluggish, that is the wrong time to cultivate the enlightenment-factor[265] of tranquillity, the enlightenment-factor of concentration, the enlightenment-factor of equanimity. What is the reason? A sluggish mind is hard to arouse by these factors.
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&quot;Monks, when the mind is agitated, that is the wrong time to cultivate the enlightenment-factors of investigation-of-states, of energy, of rapture. Why? An agitated mind is hard to calm through these factors.

Mindfulness, the Buddha notes, is to be always cultivated:

&quot;But as for mindfulness, monks, I declare that it is always useful.&quot;

http://www.accesstoinsight.org/lib/authors/walshe/wheel318.html#passage-58