Robert Pattinson's girlfriend, Kristen Stewart believes not being an 'asshole' is the key to a good relationship

Kristen Stewart and Robert Pattinson

The 21-year-old actress has been dating her 'Twilight Saga' co-star Robert Pattinson – who plays Edward Cullen, the vampire love of her character Bella Swan - since 2009 and Kristen says being honest and refusing to "take s**t" is the only way to maintain a successful love affair.

She said: "Hmm … good relationship advice for me tends to be being honest and knowing yourself. Don't be an asshole. That's my advice. Don't be mean. Don't take s**t. Don't settle."

Although Kristen and Robert, 25, share an on-screen love affair, she admits she doesn't like to watch the 'Twilight' movies with him but instead prefers to view them with Robert's fictional romance rival Taylor Lautner, who plays werewolf Jacob Black.

She told the US edition of Glamour magazine: "It’s fun to watch with him because we actually sit and watch it. Me and Taylor are actual 'Twilight' fans, so we can sit there and be totally into it! Whereas I sit there with Rob … he likes it, but he has just such a different energy."