Robert Pattinson insists he always stays grounded because he isn't very confident.

The Twilight star explained that it’s extremely easy for him to stay grounded despite all his successes because he doesn’t have enough confidence to get arrogant.

Speaking to Cosmopolitan magazine, he said: ''I'm quite an insecure person, so it's not hard for me to stay grounded. You have to be pretty dumb to let your head get big, especially when everything about your life is reported. Everyone knows you're just a vain moron.''

Pattinson also admitted that he doesn't really know what he's doing when it comes to filming movies and just hopes for the best.

He further pitched in: ''I don't really know what I'm doing when I'm filming, so a lot of the time it's like a tossing a coin if something comes out good or not.

''I can walk on to a set and have done all my preparation, but have no idea what's going to happen until I open my mouth.''