"Things can change very quickly if you let your eye off the ball.
"There are still 10 or 12 teams with a chance of reaching the play-offs. It's going to be very tight until the end of the season."
The game was settled in the 29th minute with a goal from Martyn Waghorn, who is on loan from Premier League Sunderland.
Andy King's header from a Bruno Berner cross found Waghorn, who reacted sharply to squeeze home an angled shot from six yards.
Pearson added: "It was a good win for us. I thought we played very well and were in control for the majority of the game.
"I know it was only 1-0 but I thought we were really comfortable. We played some good football and were very disciplined.
"We had to be at our best today because Cardiff are a very good side."
Cardiff manager Dave Jones refused to be downcast despite the defeat.
He said: "Every defeat is disappointing but now I can see light at the end of the tunnel. We are now getting back players like Stephen McPhail and Peter Whittingham, who are both very creative and high quality players.
"When they are all back, watch us go.
"Once we get our sharpness back we'll fly. I can see it coming but it might take a little time."
Jones conceded that Cardiff's financial problems have had a knock-on effect on the pitch.
He said: "It means you can't bring players in when you are down to the bare bones."