We have complete control over this phase. Its success depends upon willingness and concentrated effort. Incubation is the subconscious mind at work. It is not subject to the will. The subconscious does the real creative work, though it depends almost entirely on the conscious preparation that precedes it.
Illumination is the sudden flash of inspiration.
It surprises us. It astonishes us. Flashes of inspiration strike so suddenly that Plato and Aristotle associated them with the divine source of the inspiration. So do I. Verification sorts the good from the bad. Not all ideas will work.