Reading a BGG forum the question came up for Bless does the phrasing "Cast and discard" mean you discard on an unsuccessful spell check? My answer is no; "To cast a spell, an investigator must pay its Sanity cost and then pass a Spell check." Then I realized that this means every "cast and exhaust" spell would not get exhausted on a failed check. My reading of the rules seems like casting goes- Dedicate hands, Lose Sanity, Roll, Effect. Cast and… falls under efffect right?

Your sequesnce is correct…Dedicate hand(s); Exhaust Spell; Spend Sanity; Make Spell (Lore) Check; If successful, Spell takes effect and "Discard" if directed to do so or If unsuccessful, nothing else happnes…you do not "Discard" spells which don't provide an effect.