United were twice pegged back before Bruno Fernandes struck a winner from the penalty spot after an injury-time VAR call.
Amorim said afterwards: "It is three points, if you look at the game we should solve it in the first half and control the game - but we are fighting to the last minute because of things we overcomplicate. Look at the first half, we have so many chances to score. You feel you can control the game.
"But one throw-in, one set-piece. I shook my head, because sometimes football is like this. This was a game we had to win, but we have a lot to do.
“It's really important but in the future we’ll find out. It’s three points. If you look at the game we should solve the game in the first half and control it. It’s never easy, we have to try to fight until the last minute. I think we overcomplicated it. For me, the most important thing is that no matter what happens, we try. Sometimes we play well, too open, too fast, losing possessions, but the effort is there.”
Players' efforts
Amorim admits he was pleased with the passion shown by his players as they battled to the end.
He also said, “I was frustrated like any Man United fan, we had chances to score more goals, create more chances. Today, the football was fair - we were the better team. Some moments are really decisive. Sometimes we were not playing so well, but you can see the effort of everyone on the pitch wanting to win.
"If you look at the first half we have so many chances to score a goal and that can help us control emotions, the fans, but we are always doing this. One throw-in, one set-piece and at this moment it’s hard for us. I’m shaking my head, because sometimes things are really easy, sometimes not.”