Jean-Christophe Bahebeck had put the hosts in front before a late Mauro Icardi brace earned the win for Inter.
“Of course we can work very hard and not get points. We worked very hard for the last three weeks, but in the end we could've drawn or lost this game too," De Boer told Sky Sport Italia.
“There were some good things we can build on in future. I saw a team that wanted to win and that is already very important for me. We played very well in the first half and the three Pescara chances were from our errors."
De Boer surprised by making all three substitutions 15 minutes from time, introducing Eder, Stevan Jovetic and Rodrigo Palacio.
“After going 1-0 down we were too wide and Pescara could've scored a second, so I preferred to have three sets of fresh legs and refresh the team.
“I thought the first 20 minutes of the second half were the best we've done all season, but after we lost the ball in a foolish way, we lost our heads, so I thought it important to introduce three players and shake things up.
“In the end I think the victory was deserved. If you analyse the chances Pescara had, they were always our fault. When you give the ball away, then it will always be difficult. I think if we improve in that, then we'll limit the chances for the opposition because they won't have the ball.
“I also think it's important to mark preventatively, as we needed Samir Handanovic to make some crucial stops in certain situations. He was extraordinary today again.
“Football is about small details and I saw some good things tonight. With good players, you can play any kind of system."