Johnstone made a couple of crucial saves in the second-half to keep Palace within touching distance of Spurs, but the Eagles couldn’t get the crucial equaliser.
“Frustrated not to at least get a draw,” he said after the game. “I thought we played well. It’s a tough place to come but we played well and we deserved more out of the game.
“[The manager told us] that this is a club that spends a lot of money. They are a big team. He thought we were the better team and we were unlucky with the score.”
Despite Palace no longer fearing relegation, Johnstone says the squad remain as motivated as ever to perform each week.
“Any footballer will go out on the pitch to win the game,” he said. “That’s what we are still doing even though we are safe.
“It showed today: even though we lost, we put in a good performance and we were unlucky.
“I waited for my chance and now I have to keep taking it with both hands. Goalies work together every day and we support each other no matter who is playing.
“At the moment I am playing and [Vicente Guaita] is supporting me. It’s nice to be on the field getting minutes and hopefully it will continue.”