Jessie Cave: The Harry Potter actress and stand-up talks obsessive fans and living the sitcom life

I was just a small part of the Harry Potter franchise When I got the audition to play Lavender Brown in Harry Potter and the Half-Blood Prince six years ago, I'd only done a few ads before, including one for Veet hair-removal cream. Winning the part felt like winning the Lottery.

Rejection defines the acting profession When I started acting, it affected me a lot. But after a few years of dealing with it I've realised that it has made me calmer person, as I've become used to dealing with upsets. Now I'm ridiculously optimistic in a profession that's filled with desperation.

I still get Harry Potter fans approaching me The fans love the series so much it's like a hobby. I was doing warm-up gigs upstairs in a pub for my stand-up show Bookworm recently, and these teenagers found out and came all the way from France in these special fantasy-style outfits to watch. They'd made such an effort and it wasn't even related to Harry Potter; obsessive fans put in high levels of effort.

I don't enjoy doing stand-up I see it as being like exercise: I feel good about it after I've done it. I hope to get to a point where I do look forward to it, but I've got a gig tonight and I'm already shaking!

I'm obsessed with books When a good book hits me it's all I can think about and all I can do. I love Stieg Larsson's Millennium trilogy, and in particular the character Lisbeth Salander. She's the polar opposite to me, as I'm so uncool and chubby. She's this cool, strong character who doesn't need anybody; she's a lone ranger and she wouldn't get affected by things like a guy not texting her back, like I do.

I'm doomed romantically I try to find a formula for everything in life and that includes romance, but my methods haven't proven successful because there is no formula in romance. I've mistaken lovely texts or tweets for something they weren't and I was really upset once when I thought I was getting close with one guy. With social networking, it's easy to fool yourself into thinking you've established a connection when you haven't.

'Roseanne' has informed everything I do in life I watched every episode [of the American sitcom] as a kid and I came to realise that my mum is just like Roseanne: she's funny, dry and suffers no fools. She's the ultimate matriarchal figure.

I grew up in a car I have five brothers and sisters, and as my older brother and I both played tennis nationally, my mum would always be taking us to the next tournament. Even the three little ones would have to come, eating cereal in the back of the car as we drove around. I was naturally quite good as I was big and powerful, but I didn't enjoy it and luckily I got injured when I was 15, so didn't have to do it any more.

Andre Agassi was my dream man when I was growing up I wore the same tennis clothes as him as I was a bit of a tomboy. He was a heart-throb, but did you know that his long hair wasn't real? He wore a wig as he was too scared to admit to the world that he was going bald. Then he met Brooke Shields [whom he married in 1997] and she told him to take it off, and he did.

People suit their star sign If someone is annoying me over and over, and I know they're a Sagittarius, say, I'm more likely to forgive them. It comes down to my need for structure as a way of finding my bearings with people.

Jessie Cave, 26, is an actress and stand-up comedian. As part of Channel 4's annual drama-talent initiative Coming Up, Cave will be appearing in TV drama 'Burger Van Champion', on Channel 4 next month