The Royals signed off from their brief top-flight return with a 4-2 defeat at West Ham.
Nigel Adkins' side had fought their way back into the match with a quickfire double at the start of the second half, when Blackman had been one of two substitutes, only to then let the Hammers off the hook following a spell of pressure as captain Kevin Nolan went on to complete his hat-trick.
In a way, the 90 minutes at the Boleyn Ground summed up Reading's season back in the Premier League, where errors at the back proved fatal despite providing a decent goal threat.
Blackman, signed from Sheffield United in January, is confident the lessons learned will prove key to the Berkshire club's hopes of mounting a sustained promotion assault once again.
"People are very frustrated with how the season has gone, and against West Ham kind of typified it, when we got ourselves into a good position and then could not hold on," Blackman said.
"The squad are determined to make sure that is not the case next season.
"We have to learn that when we do get into winning positions, we have to kill the game off - we were 2-2 against West Ham, had them on the ropes when we had a couple of more chances, but did not kill them off.
"That is the difference, we have to be ruthless in both boxes. If we take that into the Championship then we will be in a very good position this time next year."