The quote suggests that each individual possesses an inner sanctuary, a deeply personal space that reflects their unique identity. This "little fortress" symbolizes a place where one can be entirely authentic and true to themselves, shielded from the external world's influences and judgments.
The reference to it possibly being the "soul" underscores the idea that this private space is sacred and integral to who we are. It emphasizes the importance of maintaining this inner world, as it is essential for one’s sense of self and individuality, distinguishing us from others.