United and City finished normal time 1-1, ahead of City winning the penalty shootout.
Ten Hag said, "I was very pleased. After half an hour we were very competitive and we came in the fight and we were passionate in the fight and that is what we demand from our players. It was very good and we can take this into next week (against Fulham).
"The league start is the most important. I think we can take a lot of positives from this game, and it will give us confidence but also a little bit of pain in our stomach. When you are twice leading - in the game and in the penalties - then you have to feel the pain. We were very close but (did) not (win) a trophy.
"I missed (our fans) so much. I am so happy we are back. I am really looking forward to the season. Starting on Friday against Fulham. We have some days to prepare and we have to use them. We have to use them and start against Fulham.v
"We worked and we had a competitive team. That is the responsibility for all of us. It is from players in the first place to be available and then for the staff to work with them, to support them, make them fit and keep them fit. When players are available we have a very good team."
Ten Hag added: "We are going in the new season. I am very pleased with the new structure. We are working very good together. The team was always good but I think we can make steps forwards. I think from pre-season, and also today, we can take positives but I think if we step up and are more clinical in both boxes, then we can be a successful team."