Mayor de Blasio urged troubled city cops to seek help from ThriveNYC amid the NYPD’s suicide epidemic — days after the mental-health initiative spearheaded by his wife bailed on an event for first responders, The Post has learned. “There is no feeling worse than wanting to help someone and not knowing how,” wrote de Blasio in a department-wide e-mail, a copy of which was obtained by The Post, in which he recounts losing his World War II-veteran dad to suicide when the future mayor was 18. “Yesterday, we lost our eighth NYPD officer to suicide this year,” wrote de Blasio...