I am specifically wondering how to best blend the main character's past with the decision he faces in his daily working life and would like to explore different options (from direct blatant past vs present comparisons) to more subtle ones. Any suggestion, especially from short stories, is welcome!
We really need a spoilers tag, so we can use examples without spoiling things.
The example I'm about to give spoils a major plot point early in FullMetal Alchemist. Don't read any further if you plan on reading/watching FullMetal Alchemist.
Last warning, FullMetal Alchemist spoilers ahead.
Early in the series, Edward and Alphonse are searching for a philosopher's stone. They recruit one of their friends into the search. This friend stumbles upon a nationwide conspiracy revolving around philosopher's stones, and is murdered by the people behind said conspiracy. Ed and Al blame themselves for their friend's death, and vow to not get anyone else killed for their quest. This decision comes back to bite them when later they purposely avoid asking for help out of fear of dragging more of their friends into dangerous situations.