Only now are Manchester United seeing the best of the Bulgarian - two years after his £30.75million move from Spurs.
Berbatov has seven goals in six games this season.
The 29-year-old admitted: "You try not to think about it but sometimes you just can't help it. You start thinking, 'It's a lot of money and what's going to happen if you don't prove good enough for that amount of money or you don't score enough goals?'
"They're always going through my mind and sometimes it can be bad for your concentration and your skills because it distracts you. You start to underestimate your skill which is not good because I know what I can do.
"But every player has periods like this and the main thing is to stay strong because you are going to have dark moments.
"In the end I just say, 'Relax, play. You're playing for the biggest club in the world' - nobody can say anything else."