The Northern Ireland international said: "No-one likes to be in the bottom three. We didn't close the game out against Derby and that is something we need to learn how to do.
"We haven't won for a while. In the previous home game against Chelsea, you would have settled for a draw after holding them for 80 minutes and again we conceded late on.
"You've got to be able to see the game out and keep a clean sheet. It was the same again versus Derby. Once we got the goal, we should have been more precise in seeing the game out.
"Late goals do kill you and it is something we need to eradicate. The performance was quite decent but it has all ended a bit disappointingly."
Blues have several players in their side who have never before experienced the pressure of a relegation battle, and Johnson knows they have to learn how to cope with the situation.
He said: "It is a tough position to be in but they have to grow up quickly and I am sure we have the right type of characters in there to come through this.
"It is just about keeping up the performances like we have shown recently, apart from against Sunderland, and seeing games through.
"That is basically the bottom line. We just need to dig in and hang in there and drag ourselves out of this situation."