United were punished for not taking a number of chances as Luuk de Jong made it 2-1 with twelve minutes remaining in the match.
"It's one of them if you take chances you win comfortably - not always the case in football," Solskjaer told BT Sport.
"We had moments in spells in both halves where we should have scored a few. We have a young team - some spells showed that this group of players will have to learn and get some consistency in their play.
"When we get the ball down and create chances it's scintillating at times. The keeper had a fantastic game. It's disappointing we didn't score because we've got players with that quality.
"Since February we've been fantastic. Then again it's disappointing to go out. We've come quite a distance. Exciting to work with the boys but you could see at the end - tired legs and tired minds. We definitely need to improve to move up the table and take steps in the cups. I've never had three semi-finals in one season."