How are progressed aspects to other progressed aspects more/less significant than progressed to natal aspects?

Allright, well I was under the impression that progressed aspects were only relevant in terms of how they relate to the natal chart...so I'm at a bit of a loss here. The progressed aspects, which usually do happen first would signify the inner psychological change needed for the individual to prepare themselves for the later outer manifestation of that change which would be indicated by aspects from *transiting* planets to the natal chart. Maybe someone with many years of experience will come along and clarify this for both of us:-D (if they haven't already-i type slow)