Literature is a strategy for postcolonial survival because it gives postcolonial people a voice. "Postcolonial" refers to the point-of-view of the oppressed; it is the view from below.
Being able to tell one's own story is empowering. For postcolonials, such storytelling is a way to push back against the way the colonizers have characterized and stereotyped them. Writers such as Rudyard Kipling valorized white culture and the white presence in colonized nations as a "burden" the Europeans carried for the benefit of civilizing the ungrateful natives. In telling their version of this story, the colonized can express how being occupied by violent and unjust invaders damaged them. Blacks in the United States likewise can push back against stereotypes that they were "lazy" by describing how discouraging it can be to know that no matter how hard you work, you can never get ahead. Native Americans, often stereotyped as "dishonest," can express how they needed to lie to protect their culture or explain how European concepts of land ownership were alien to them and so misunderstood.
Writers such as Franz Fanon argue that postcolonial peoples cannot achieve real freedom until they shed the internalized "white" values of the colonizer and begin to discover who they are independent of European thinking. Otherwise, they will carry around feelings of inferiority that have been imposed on them and try to imitate white ways of exploitation and consumption that are damaging to themselves and their people. Telling their stories is a first step in regaining power over their lives.