Providing a goal and two assists in their 5-2 Premier League win on Tuesday, Alli was pivotal as Spurs kept pace for Champions League places.
"We speak a lot, the manager and myself, and my form is not really something I think about too much," Alli said. "But it's always nice to prove people wrong.
"At 21-years-of-age when you set your standards as high as I did the last two years it's not always the case that you're going to reach them all the time."
In three appearances in the Champions League this season, Alli has notched up two goals and three assists.
His goal against Southampton was the first in 10 matches. However, according to Alli, goals and assists are not the sole indicators of performance.
"Some people think if you're not scoring or assisting you're playing badly, but I think I criticise myself all the time," he said. "I think it's just working on myself and my own game.
"As players we're not too worried about what people are saying, as long as the people close to you, around you and your team-mates are speaking highly and you're doing what the team wants, that's all you need to think about."