The 29-year-old has netted six goals in six games since his £4million arrival from Everton in the summer, but the Blades have so far won only two of their six league games and Beattie wants to see an improvement.
They drew 2-2 with Blackpool on Tuesday night, while Beattie also cited the 3-2 loss at Scunthorpe as a missed opportunity.
"We have to be more ruthless. If we want to get promoted then we have to start going to places like those and winning, particularly when we go in front," he told the Sheffield Star.
"No disrespect to either Blackpool or Scunthorpe, but we need three points from these games and we knew that's what we needed to achieve."
"We've got to keep the ball more and pass it better because the quality is there. But we will get there, that's for sure."