Yeah, this has been mentioned by others, but it's without doubt the most important technique I've learned to employ. I was not diligent at this when I was learning as a young kid, in any style of music. So I got pretty good (since I was just able to power through certain pieces and solve technical problems, with the aid of a very good teacher in an ad hoc fashion), but as an adult when I no longer studied with anybody, there were difficulties in expanding my technical and analytic abilities.
One could call it an abstraction, or a hyper-fragmentation while learning different pieces: the reasons could be to improve memory, or to solve some mechanical problems, or other things.
A piece of music must have a unified conception, of course — after all, one must have something to play, and ideally it should be at least pretty good, or at least good enough (!) — but in dissecting and learning a work, I find it better to be able to begin and end at any part of the music, and often in rather small units.
Theoretically, dividing the work into smaller pieces, or smaller concepts is not dissimilar to George Pólya's strategic plan outlined in his famous handbook, How To Solve It. And in music as well, it is entirely oriented as a practical method. That is, one to be practiced.
In other words, don't play what you know, as in start from the beginning of a piece doggedly and then get tangled up. Isolate the fragments that are confusing or difficult, whether intellectually or mechanically, and find solutions.
I would say it's a strategy based upon, in the case of music, perhaps very literally a "de-composition," since I imagine that is how some composers of through-composed music conceive of certain aspects of their art.
So, tactics at the level of the "cell" or the individual moments, but employed with an idea of the entire plan, as one can also employ simultaneously by "playing" or, even better, "hearing," such-and-such a piece in one's mind away from the keyboard, as ranjit demonstrated in an above post with which I also agree very much.