Martin Short has always shown an "unbelievable" level of "resilience".

The 76-year-old actor has had his fair share of setbacks both professionally and personally, including the recent tragic death of his daughter Kathrine, who took her own life aged 42, and now his longtime friend Lawrence Kasdan has opened up about the Only Murders In The Building star's mental strength.

Lawrence, the director new Netflix documentary Marty, Life Is Short, told Deadline: "The key word to me is resilience.

"I think that's the key to all careers because inevitably you're going to be disappointed, you're going to have flops, but how resilient are you? How quickly do you get back up?

"And people like to say, 'Oh, I always get back.' But they don't. People don't always get back up, and you can take it one way or another, and you can be more or less damaged by criticism.

"And Marty just seems to have this resilience that's unbelievable. And you see it in his personal life, of course."

In the documentary, Martin says his career "has been 80 percent failure", adding that "those are pretty good odds".

The film tells the highs and lows of his life and career, and Lawrence is glad to see the different levels resonating with viewers.

He said: "I'm glad that people react emotionally to it because it is emotional material and he's a good guy, so you're really invested in him.

"The thing that amazed me about him, that made me do this, was that spirit that goes through anything. So, it just got more and more poignant as the making of the film went on."

In his personal life, the star was just 12 years old when his eldest brother David died in a car crash, and he was 18 when his mother died of cancer, while his father passed away two years later.

In 2010, Martin's wife Nancy Dolman died of ovarian cancer aged 58, and he has had more grief this year following Katherine's death.

Last month, the actor reflected on his grief for the first time in an interview with CBS News Sunday Morning.

He said: "It's been a nightmare for the family. But the understanding [is] that mental health and cancer, like my wife's, are both diseases, and sometimes with diseases they are terminal.

"And my daughter fought for a long time with extreme mental health, borderline personality disorder, other things, and did the best she couldn't until she couldn't.

"So, Nan's [Nancy's] last words to me were: 'Martin, let me go.' And what she [Katherine] was just saying [was]: 'Dad, let me go'."