The Gunners were second-best for much of the game, being bullied into a comprehensive 3-0 home defeat against a Seagulls side oozing with confidence.
Second-half goals from Julio Enciso, Deniz Undav and Pervis Estupinan earned Brighton a third win on the spin at the Emirates Stadium, and means Chelsea will win the title if they beat Chelsea next season.
"Yeah, it feels like [the title is over]," Odegaard told Sky Sports. "It is going to be very difficult now, we have to be honest. It is tough to take.
"It is not a good feeling at the moment. The way we played, particularly in the second half, I don't know what happened to be honest. It feels like there is no hope now.
"In the first half we did a lot of good things and had moments to create big chances but we gave them more and more momentum in the second half.
"We wanted to come here and continue like we have in the last two games, get a good result and keep pushing. It is a big disappointment [in the dressing room].
"I don't think mentality was an issue. We were good going into the game but in the game was a different story and we have to accept it and learn from it."