The screen star - who is best known for his role as Edward Cullen in the vampire franchise - admitted that he has run out of steam at the right time as the final installment of the film is released later this year.
He told ShortList: "Playing the same part for a while, you just run out of ideas. You feel kind of useless, you don't know what to do anymore.
"I'm not trying to get away from it. You're screwing yourself, you're saying you think your work is s**t if you try and get away from it."
The 26-year-old reiterated: "And I never thought it was [s**t]. But I kind of got to the end of my inspiration."
Robert appears in 'The Twilight Saga: Breaking Dawn - Part 2' - in cinemas November 16 - alongside Kristen Stewart (Bella Swan) and Taylor Lautner (Jacob Black) and is looking forward to future projects.
He added: "You get to the point where you're like, 'I don't want to do a film for a teen audience anymore'."
Here's the "Twilight Saga: Breaking Dawn Part 2" trailer: