After a stoppage-time sucker punch had led to defeat at Derby and a last-minute leveller cost them victory at Birmingham, Karanka was sickened by an 86th-minute Matthew Upson header from a corner which handed the Seagulls the victory at the Riverside and left Boro just three points above the drop zone.
"Yes, of course I am angry," he said.
"We are giving gifts to our opponents in every game.
"I can't believe it. It is the same thing again. It is not normal to play so many games when you are probably better than your opponents but you do not get the points.
"The most important thing at set-plays is for a man to know who he is marking and to stop them from scoring goals. That is it. That is the job at set-plays.
"It is always a lack of concentration. It cannot continue in this way. Here we are again after five games now saying the same things.
"All we can do is work hard. The biggest problem though is focus. My hope is that in the next games the players concentrate until the very last minute. "
Brighton assistant head coach Nathan Jones admitted the late smash-and-grab win was a huge boost for his side and their hopes of climbing into the play-off places.
"Every win is a big win in this division," he said.
"But to come to Middlesbrough and win is a very good result.
"Believe me, and I'm not being condescending, but they are in a false position.
They are a good side who should be higher than they are in the table, so it was a massive three points for us.
"And it wasn't easy. We started well in the first 20 minutes but after that we had to grind it out. We weren't fluid and they had a lot of possession in the second half.
"They were playing well but we tried to win it and we made a few positive substitutions, so it was ironic we won it with a set piece.
"It wasn't the way we planned it but we'll take that."