What's actually happening
A Full Moon happens when the Moon stands opposite the Sun from Earth's point of view. The lunar face is fully illuminated. A Full Moon in Capricorn means the Moon is in Capricorn while the Sun is in Cancer — the axis of the structural and the emotional, of duty and care.
The geometry is one of maximum contrast between what has been built and what it has cost.
What the tradition makes of it
Full Moons are culmination points. What was seeded at the New Moon has enough light on it to be seen. Capricorn adds a quality of sober reckoning to the culmination: the achievement is assessed against its actual cost, the structure is measured against the purpose it was built to serve, and the long work either justifies its investment or reveals that something has been built out of proportion to what it was for.
The Cancer Sun asks what was nurtured and cared for during the building. The Capricorn Moon asks what was produced. The tension between them illuminates where the ambition has been in or out of proportion to what genuinely matters.
How to actually use it
Assess what has actually been accomplished — honestly, without excessive self-criticism or self-congratulation. This is good weather for acknowledging what the work has produced and for recognizing what, if anything, was sacrificed in its service that did not need to be.
When in doubt
Ask whether what you have built is worth what you gave up to build it — and if not, what that tells you about the next commitment.