Heung-min Son hit the post moments before Fulham's goal, as the match followed a similar pattern to Spurs' frustrating 1-1 draws with Crystal Palace and Wolves, and the 2-1 defeat to Liverpool, when Mourinho's side missed a string of chances.
"In the first half we had chances to kill the game – some of them are [Fulham goalkeeper Alphonse] Areola's responsibility," Mourinho said.
"In the second half we had the biggest chance to kill the game but when you don't do it you cannot concede goals the way we did do it.
"This is the same story basically since the beginning of the season. We can talk about not killing the game yes, we can speak about that, and today was a clear situation where we could and should have killed the game in the first half but then you go back to the goals that we concede and it's not also easy to assimilate that."
Davinson Sanchez was turned by Fulham Ademola Lookman and Cavaleiro climbed above Eric Dier to meet the substitute's cross in a bad moment for Tottenham's centre-backs.
Asked about their lapses in concentration for the goal, Mourinho said conceding was down to the "individual ability" of his defenders.
"I think there are things that have to be with the characteristics of players," Mourinho said. "There are things that are difficult too. There are some things they have to do with organisation of the team, but other things they have to do with individual skills, individual ability, and its as simple as that."
The contest assumed the proportions of a grudge match after Mourinho and Scott Parker clashed over the Premier League's decision to reschedule the fixture for Wednesday at 48 hours' notice. Parker called the decision "scandalous" while Mourinho said the Fulham boss should apologise to the rest of the Premier League if he fielded his best side, which he did.
"I know the top hierarchy at Fulham Football Club and we're dealing with honest people and of course they had problems," Mourinho said.
"Of course the reason why we didn't play the game when we should, there were reasons for that. Let's put that very, very, very clear.
"The reason why they were not happy to play today is a different questions you have to ask Scott, not me. But in the football world it's very difficult to keep secrets. Somebody tells somebody who tells somebody who tells somebody and it arrives to somebody else.
"And of course we knew for a few days that they were ready and had the players to come. [Aleksandar] Mitrovic is not a Covid situation, [he] had a small injury from the last match. We knew that so it's something you have to ask Scott. But make things very, very clear. Of course they had problems and of course there was a reason for them not to play the game a couple of weeks ago."