David Unsworth believes Sunday's match against Watford is crucial for both him and the club as he aims to secure the role of full-time manager.
The academy coach, 44, was placed in caretaker charge after Ronald Koeman's sacking, and ex-Everton player Phil Neville told BBC Sport he thought he had four games to prove himself.
However, he has overseen three defeats and Europa League elimination.
Unsworth said: "Watford is a huge game for me and the players as well."
Thursday's 3-0 defeat in Lyon, which resulted in the Toffees' exit from European competition, was the club's fifth loss in succession - their worst run in 12 years.
The result in France also meant they became the first English side not to win any of their first four games of a Europa League campaign.
"When you're not winning games, you do concede sloppy goals and have a little bit of bad fortune," added Unsworth, whose side are third bottom of the Premier League.
"So the mentality must be strong and we must have the courage to be strong if we go a goal behind, the courage to stick together.
"Confidence is a great word in football and you only get that from winning."
On Wednesday, Wolves boss Nuno Espirito Santo ruled out taking over at Goodison Park amid reports of interest from the Merseyside club.
Earlier this week, former England manager Sam Allardyce said he would consider an approach from Everton.