Fortune in the 12th House
Things kept out of sight and time spent alone are where this luck actually settles. Don't rush to announce anything; give yourself quiet space, since the answer usually surfaces after it's had time to sit.
In detail
This form is established when the Lot of Fortune falls in the 12th House at birth, fixed by the day or night formula. The 12th House traditionally governs hidden matters, solitude, and behind-the-scenes affairs, so Fortune here tends to surface quietly, after time rather than through open display. This is the reverse of the 10th House, where the resource sits in public standing rather than out of sight.