Reading are still searching for their first Premier League win of the season and sit bottom of the table after four games.
But McDermott insists they have been lifted by Wednesday night's 3-2 Capital One Cup third-round victory over QPR.
"It was a really good night for us, especially after the last two league games where we felt we hadn't done ourselves justice," he said.
"We stripped the team back to what we're about last night. Everyone could see we had a real identity.
"It's about being close as a group. Last night we attacked and defended as a group. Doing things together is the ethos of this club.
"Everyone feels better about themselves after last night. It's tough because we're not used to losing games here. It's not something we like doing."