In an encounter at the Artist's Colony, you can prevent a young girl whose boyfriend has died from committing suicide. It raises your Sanity.
You can protect Velma from some hooligans. In gratitude, she lets all investigators eat at her diner for free for the rest of the game. note Mechanically, any encounter at Velma's Diner in which she offers food that restored Health and/or Sanity may be taken without paying, and can restore as much as the game allows.
You can watch a man paint his girlfriend. Watching it restores Sanity.
Many of the Another Time encounters. You might visit a childhood playground, see your mother and father as a young courting couple, or even see a statue of yourself in the far future and know that you made a difference to someone. These all restore Sanity.
Completing Personal Stories in a successful way will often make the player feel good. For instance;
Jenny Barnes finding her sister Isabelle alive and well.
Wendy Adams finding her long-lost father.
Rex overcoming his curse and finally getting the proof he needs.
Darrell finally getting respect from his editor.
Wilson getting that Tagalong Kid friend of his safely out of Arkham.