The Premier League giants were battered at home by the current league leaders on Sunday.
After the 6-3 humbling at the Tottenham Hotspur Stadium, Kulusevski admitted they had to change if they wanted to win trophies.
Kulusevski said: “You have to improve, you have to find ways.
“Maybe today we should maybe let them have the ball more, but you know, that's not how we play. So we went out, we gave everything. It didn't work, maybe we (will) learn for the next time.
“You have to think about how are we physically? Who's playing? How many games have we played in the last week? Who are we playing? Have they rested for one week or something?
“You have to put everything in because it is like life. It's not just black and white. It's a lot of factors going into it.
“We have to learn because we conceded six goals. I can't sit here and say that we're doing something perfectly, we're not. We have to change a little bit for the better, always try to change for the better.”