Former AC Milan, Juventus and Italy star at the weekend announced he will end his career when his New York City FC contract expires at the end of the year.
Pirlo won six Serie A titles, two Champions Leagues and a World Cup with Azzurri.
“You realise that the time has come,” Pirlo, 38, told La Gazzetta dello Sport.
“Every day you have physical problems, you cannot train as you want because you always have some problem.
“At my age, that’s enough. It’s not that you can go on forever until the age of 50. I’ll do something else.
“At 38, it’s just right to give young players room. I’m not angry. Instead, I will give a hand to team-mates and to the coach,” he said.
Pirlo also spoke on talks that he could go to England and join fellow countryman Antonio Conte at Chelsea.
“I’ll do something else, I’ll be back in Italy in December.
“Work with Conte? They say things, I have some ideas, but give me time to decide,” he added.