Nick Woltemade fired Newcastle in front before Arsenal struck an equaliser on 84 minutes through Mikel Merino ahead of Gabriel Magalhaes' 96th minute winner.
Tonali said afterwards: "It is difficult after this game, in the last five minutes to lose. But we are professionals and we have to change as quick as possible.
"We played a good game, especially in the first half. We were concentrated all the time. I think it was a good battle in the midfield but we need to have the maximum concentration in all the 90 minutes. I want to take positives into the next match.
"It was similar (to the Liverpool match) but I think we want to win the game until the last minute. I think sometimes we need to put some experience and maybe today a draw was the perfect result. It is easy to speak and I think we played a good game."