Books where the main character thinks their life is worthless but they end up being the important character who saves the day?

After having seen a recent movie that came out (D&W), I fell in love with this specific trope (albeit I don't know what the name of said trope is). The main character deals with self-esteem issues, believing they're worthless or don't matter to anyone or anything, having no purpose, etc, then through the hero's journey they discover their purpose, that they do matter, and they are the ones who save the day / city / world / multiverse.