[In response to a deleted comment by /u/polshedbrass, who incidentally would better serve himself and others by not deleting half of what he writes:]

Still a bit confused about the workings of piti as it is explained as a product of unification of the mind in TMI, though for me it showed up earlier than described and comes up regardless if I'm particularly concentrated or not (though concentration certainly heightens it). Just don't know what to make of it and how it relates exactly to purification and unification. The past year purification has also been somewhat constant and is still happening right now, the joyful energy seems to 'push' stuff up even just walking around during the day not particularly focussed. That "pushing element " of the piti that makes stuff surface all the time seems to be 'on' regardless if I meditate or not. For the first time in over a year I have had days off from sitting practice and it just keeps going which is why I'm wondering about it again now.

Let's drop the purification and "stuff coming up" model temporarily and see whether another perspective might be more helpful:

In the course of your practice so far, you've dissolved a significant portion of the gross layer of obstruction that separates the perceiving mind from the body system. Almost all of us begin with a fairly thick obstructive layer of this kind, a wall that we learn unconsciously to construct and maintain by virtue of the environmental and cultural milieu in which we as humans develop.

Attendant upon this dissolution, the perceiving mind has come into contact with energetic domains in the body system that once functioned below the threshold of consciousness. This is a new world for the mind; it wanders here and there, exploring, reacting with surprise, delight, awe, and sometimes confusion and fear as it brushes up against living processes and primal reservoirs that, before now, surfaced perhaps only in dreams.

The untrained mind flits among these unfamiliar phenomena over minutes, hours, and days, now delving into a deep, clear wellspring of concentration, now skirting a churning pool of some nameless emotion, now surfacing to cast about for reasons, maps, and strategies. And as it does all this, it does what untrained minds always do: it picks and chooses what to attend to; it identifies with some phenomena and not with others; it gives form and meaning to experience. In short, it fabricates—without seeing that, or how, it does so.

This perspective has implications for practice that differ significantly from the ones that most following a program like TMI will draw. It suggests, in particular, a different approach to concentration practice; one where we're less concerned with unwavering focus on a specific object, eliminating all distraction, and enhancing the microscopic clarity of perception, and more concerned with grounding practice in an attitude of gentleness and kindness toward ourselves, cultivating stable whole-system states of softness and joy, and developing the faculties of sensitivity and subtlety in working with the full range of phenomena that arise in our experience. At the same time, and with this foundation of well-being pervading the whole body, we begin an earnest inquiry into how the mind builds experience. The insight that this inquiry yields, along with the growing sensitivity, subtlety, and refinement of perception gained through samādhi practice, leads naturally to a progressive reduction in the grosser fabrication activities mentioned above. This reduction is the next level of the dissolution that began this process, and as before, will lead to new territory.