Robin Williams "didn't always feel" like a success, according to his son.<br /><br /><br /><br />The late actor suffered from severe depression before his death, and his son Zak, has opened up about the doubts his father had about his own career.<br /><br /><br /><br />As seen in the first trailer for upcoming HBO documentary 'Robin Williams: Come Inside My Mind', he said: "My father didn't always feel he was succeeding, but he was the most successful person I know."<br /><br /><br /><br />With director Marina Zenovich at the helm, it looks to give fans' an insight into Williams' life, as he admitted to suffering from a childhood fear of abandonment.<br /><br /><br /><br />In a previously recorded interview, he said: "Yeah, it's a primal fear for any child and it dictates a lot of how you deal with life."<br /><br />
