Mourinho singled out Ndombele in the 1-1 draw at Burnley last season and omitted him from the matchday squad for the last three matches of the Premier League campaign.
Sources told ESPN that Ndombele was so upset he didn't want to play for Mourinho again, but he has since bounced back and impressed with his performances this term.
"It was just something that I assimilated and took on board. Of course it's not something that you like to hear, those sort of words, but that was last season and we are looking to the future."
The club's record signing has featured in every league game this season and said his form has improved because he is playing regularly.
"I feel better," he added. "That comes from playing consecutive matches. it's good for a player to have a good rhythm like that and get into shape.
"Last year I didn't have that so much. This year I do so it's better for the team and it's better for me.
"Between France and England there's a real difference in the intensity of the matches. Last season my head just wasn't in the right place. This season it's going a lot better."
Spurs are in fifth position in the table after picking up their third consecutive away win at Turf Moor. Mourinho's side are two points off the top and Ndombele is confident they can challenge for the title.
"Our objective has always been to get into the top four," he said. "More than that? Why not? But nobody wins the league in six matches.
"Even if we were top of the league at this stage there'd still be 32 matches to play."