The actor, 43, on Britishness, growing older and the importance of being wrong

The older you get the less memory you have. I have trouble differentiating between what are childhood memories and what I may have seen in a photograph or been told about by my mum. Do I really remember lying in a hammock on a beach in Puerto Rico when I was a year old?

I feel both British and American. After spending a year in Puerto Rico, my family moved to London. I spent my formative years in the UK, only moving back to Michigan when I was 11. I was initially excited about the adventure; I hadn't taken into account just how alien American culture would be and how much my "Britishness" would set me apart – but it did.

The X-Files went on for a long time – nine years – but it now feels like such a long time ago. I look back on those days with awe and gratitude. I didn't notice how huge it was at the time – we were shielded from the outside world while filming. The only time the paparazzi would show up was if there was a scandal – me getting a divorce, or David [Duchovny] dating Winona Ryder.

I have mellowed over the years. I always needed to be right, but I'm now more accepting of being wrong. It's taken a very long time to admit that, as most of my family will attest.

I pick and choose what I read about myself because of how deeply it affects me. Frank Rich of the New York Times wrote such an unfavourable review of The House of Mirth, and of me, that it literally made me want to stop acting. I was only 27, and my feet weren't as firmly underneath me as they are today.

I fear waking up with regrets. The idea that I might be doing something now that I'm unaware of, that I will have bottomless regret about in the future, keeps me up at night.

My mantra at the moment is: "What you are is what you have been, what you will be is what you do now" – I have no idea where it comes from, but I try and think of it on a regular basis to motivate me.

It was easy to have children, but it's not easy to be a good parent. I was 26 when I had my daughter, and I would have been a very different person had she not come into my life. Her arrival grounded me with a certain responsibility. Had I not had her, I think I would have taken full advantage of being young and carefree.

The last time I cried was yesterday. My younger brother Aaron is dying, and I'm currently back at home with my family. It's an extraordinary time.

I've allowed myself to be happier. The past four years have taught me to lighten up. I've learned to get out of my own way and that it is OK to feel good.

I do have a sense of humour. I'm perceived as being a bit spiky and serious, but I've been misunderstood. When I started doing talk shows and interviews I felt so out of my depth that I didn't laugh or joke because I was petrified. It has taken me decades to get used to the whole nature of fame – to allow myself to be myself in public.

Johnny English Reborn is out on 7 October