With United struggling in 13th place and losing five of their last six home games, Amorim acknowledged that sticking to his system without adding attacking reinforcements was a gamble.
He conceded that poor results have increased the pressure on his position ahead of their FA Cup clash with Leicester.
“I knew when I chose this profession that you have the risk of results,” said Amorim.
”We are fighting for our jobs until the summer.
“I knew when I came here, I looked at the schedule, I looked at the team, and I understood my decision of changing everything in the middle of the season, without new signings, was a danger for a coach.
“But since day one, with good results or bad results, I've had a clear idea of what I want to do and I take these risks because, in the end, I think it’s going to pay off.
“But I’m not naive, I've said that many times. This is a sport of results and we are in a difficult situation. But the board already knew and I explained all the risks. Everything that has happened, I explained to the board and they said the same thing: ‘We need to start now - we're doing that.'
"But I understand, at this moment, with a lot of losses, especially at home, that the environment is really hard. We're taking some risks, but it's the way we want to proceed. It's hard to turn things around in just a few games.
"It's going to be like that, really hard until the end of the season, but we are taking that risk, because we want a different thing in our team and different profiles. That was my decision.”