Both the statements actually imply that you were happy and took pleasure from the party you attended .
I would like to clarify this by giving definitions.
Google defines 'enjoy' as:
enjoy /ɪnˈdʒɔɪ,ɛn-/ verb
1. take delight or pleasure in (an activity or occasion).
I enjoy watching good films
Collins dictionary defines 'enjoy oneself' as:
Synonyms of 'enjoy oneself'
have a good time, be happy, have fun, have a field day (informal), have a ball (informal),live life to the full, make merry, let your hair down
Thesaurus.com defines 'amuse oneself' as:
Main Entry: delight in
Part of Speech: verb
Definition: take pleasure from
Synonyms: admire, adore, amuse oneself, appreciate, be content, be pleased, cherish, dig*, eat up, enjoy, feast on, get a kick out of, get high on, get off on, glory in, groove on, indulge in, like, live a little, live it up, love, luxuriate in, relish, revel in, savor
All these imply that whether you say "I enjoyed..." or "I enjoyed myself somewhere" it simply means that you took pleasure from there.