"Shinki-itten心機一転" means making a fresh start or turning over a new leaf - completely changing your mindset or approach. It's about hitting the reset button and starting fresh. EX. 「彼氏（かれし）と別れた（わかれた）後（あと）、心機一転（しんきいってん）に髪型（かみがた）を変（か）えました」 "After I broke up with my boyfriend, I decided to change my hairstyle for a fresh start."