Southgate insists England's gritty win over Serbia good for team spirit
England, runners-up in the 2020 edition and seeking to finally win a trophy befitting their vast array of attacking talent, started brilliantly and led after 13 minutes through midfielder Jude Bellingham's superb header.
But they created few chances and allowed Serbia, who were much improved after the break, to play their way back into the Group C game though they rarely threatened an equaliser.
"I'm pleased that we had to show a different side, we had to show that resilience to defend our box because I think as a group that really builds a huge spirit," Southgate said.
He added: "Our team ran out of some energy and that didn't surprise me because of the lack of 90 minutes that lots of the players have had... I think we can be more efficient in the way that we played in the first half, which would also help us."
Southgate said England were still a side in transition, without stalwarts like centre-back Harry Maguire, who is injured, and midfielder Jordan Henderson, who was left out of the Euros, and with several inexperienced players in the squad.
"This team is still coming together," he said. "Everybody's expecting us to waltz through. There's a lot of hard work ahead.
"We're short of certain things, we're finding the best possible solutions. We've had a very complicated run-in to all of this, but the spirit of the group was there for everybody to see tonight and we will definitely grow from that."
Man of the match Bellingham took issue with the suggestion that England's second-half performance showed a need for improvement, saying they would take the positives from the game.
"Obviously, commonly with the team there's a negative theme around all our games -- and sometimes rightly so -- but I think in this case you take the positives," he said.
"OK, maybe we had to hold on at times and suffer a little bit, but we kept a clean sheet and when you keep a clean sheet all you have to do is score one goal."