He also told reporters that any subsequent accomplishments after securing Napoli's first Scudetto in over 30 years might be overshadowed and considered less significant by comparison.
Although he led Napoli to the title and Champions League quarter-finals, speculation around the future of the Italian coach has been going on over the last weeks.
"The matter has been decided, you don’t change your mind every day," Spalletti said at his post-match press conference.
"It's a situation that has been brewing for a long time. When you work from morning to night, some matters tend to mature in your mind, because you have to put this spectacle on all the time.
"If you are not convinced that you can give everything these people deserve, it’s right to think it over. You think it over, you arrive at a conclusion and then you stick with it."
Spalletti said he had discussed the situation with club President Aurelio De Laurentiis and they had reached a resolution on the matter.
"All that needs doing is for it to be announced. I told De Laurentiis what I needed to say. There were no negotiations. After that dinner together, we emerged with everything sorted out."
Asked about having defeated all 19 Serie A teams in a single season for the first time, Spalletti praised his team.
"The quality of our football is what allowed us to stand out," he said. "It was motivating for the players because they were facing a deserved Champions League finalist and had to prove all that we’d achieved throughout the season."
Inter face Manchester City in the Champions League final.