The Magpies, who secured their League One status on the final day of last term, are currently sixth in the table after 12 games.
"We've got to remain grounded," Derry told the Nottingham Post. "If you don't and you start getting carried away then before you know it, concentration suffers as a result.
"For me, I've always said I want us to progress and we are doing that at an unbelievable rate if I am honest. It's happening far quicker than what I expected considering we completely rebuilt the dressing room.
"You have to bear in mind that last season we were only 30 minutes from being relegated to League Two. Going from that to being sixth in the table is fantastic, don't get me wrong. But we have achieved absolutely nothing yet."
Notts travel to Barnsley this evening.