Obsessed with and Preoccupied withHow to use "obsessed" and "preoccupied" correctly
The participial adjectives obsessed and preoccupied and their noun forms obsession and preoccupation take the preposition with when they suggest that one is constantly thinking about something. Avoid using for or any other preposition:
obsession for obsession with tiny porcelain teacups is a little strange.
He was so
preoccupied by preoccupied with his teacup collection that he forgot to defend Earth from the alien invasion.
Common Errors in English Usage: Errors in diction and idiom commonly made by native speakers of English
List of Common Errors in English Usage (PDF): Printable version of the complete list
Common Grammar Errors: A list of common errors in grammar (topics like subject-verb agreement and parallelism) as distinct from usage