Juventus is languishing in ninth place, with just four wins from 11 games, and was beaten 2-1 by Sassuolo and then Hellas Verona in its previous two Serie A outings.
Allegri's men face seventh-placed Fiorentina next as they seek to chip away at the 16-point gap between themselves and unbeaten leader Napoli and the Juventus head coach says his side must get into the habit of picking up three points.
"The league matches for us now are all must-win, until we find the mental continuity," Allegri said. "We have to be realistic and practical. Our matches in the league have always been open, and this is not good."
The 54-year-old hailed the quality of Sunday's (AEDT) opponent, picking out free-scoring striker Dusan Vlahovic, who has eight league goals so far this term.
However, Allegri backed his defenders to keep the Serbia international quiet.
"Fiorentina has three points more than us," Allegri continued. "It has technical players, it makes the most of the whole pitch and has a very good coach.
"Vlahovic is a good player and the numbers show it, but we have excellent defenders. We need to play the right game, both technically and defensively."
Juventus ended its three-game winless streak with a 4-2 victory over Zenit in the UEFA Champions League on Wednesday (AEDT), but Allegri refused to get carried away.
"We have to keep our feet on the ground," he added. "After the win against Zenit, we have to concede fewer goals and we need to put the last two defeats in Serie A behind us. Let's keep quiet, keep pushing and keep working.
"The match against Zenit is not a turning point, it must be normality, which fortunately we have had in the Champions League but not in the league. It is a mental growth that we have to do. You win a game, you put it aside and think of another."
The Bianconeri boss wants his side to be more ruthless in closing out games as it strives to climb the table.
"The only game in which we took the wrong approach was Verona," he said. "Our real problem is [that we] pull back when we take the lead, because that's where we become vulnerable.
"I like these challenges that we are facing now, there are many things to improve upon. Each defeat has its own story and it must be analysed well. The performances haven't been bad, but if you concede a lot of goals, something is missing."