The theme that can be inferred from both "Grown-Up" and "The Unexplorer" by Edna St. Vincent Millay is "Life never turns out as expected."
In "Grown-Up," the speaker reflects on the disappointments of adult life, questioning why they went through struggles only to end up in a mundane routine. In "The Unexplorer," the speaker expresses a sense of unfulfilled curiosity and the confinement of domestic life, suggesting that what seemed promising turned out to be less exciting than anticipated. Both poems highlight the contrast between expectations and reality.