Tom Hanks struggles to watch his hit movies back.

The 66-year-old star has doubts about his acting ability and has to "wrestle with authenticity" when looking back on his "big hit" films.

Speaking on The Great Creators with Guy Raz podcast, Tom said: "I wrestle with authenticity.

"I wrestle with the difference between lying for a living as an actor and lying to myself as a human being."

The two-time Oscar winner prefers not to watch his films again as it always leaves him with a sense of regret about his performance.

Hanks explained: "(I see) the falsehood in them. I see the loss. I see that one time, 'Oh man, I missed that opportunity.'

"And it's not because, at the moment, I chose not to – it's because, after it was done, I realised I didn't go far enough. I didn't go to the place that I could have gone.

"Then I asked myself, well, why? Was it because I was satisfied with what I had? Was it because I wasn't up enough on the text? Was it because I didn't have enough of those ideas in my pocket? Or you know, was it because I was late that day and we had to rush the shot and instead of six passes, we only got two passes at it?

"That's where the self-doubt creeps in."

Tom claimed that the 1994 film 'Forrest Gump' – which landed him an Oscar for Best Actor – as one of the few movies where he gave his all.

The 'Cast Away' star recalled: "We all sat together for weeks with (director Robert Zemeckis), and Bob was saying, 'Well, what do we make of that?'

"We started at the beginning of the script and we all talked about everything. Even scenes we're not in, and what it meant to the text. That doesn't mean your own lines.

"You must know the text, because the text is the interpretation of the theme, and the theme is why you're all there in the first place."