The Dutchman admits he must also look at himself after his side's poor run continued with a dispiriting 2-1 loss to Norwich - the side's third successive defeat in all competitions - at Old Trafford on Saturday.
United were booed off the field after a result which not only left Van Gaal facing further criticism but possibly fighting for his job, with Jose Mourinho and Pep Guardiola now both in the market for new jobs.
Mourinho left Chelsea on Thursday after Roman Abramovich finally felt compelled to act after a disastrous start to their title defence and has indicated a desire to get straight back into management. Guardiola will be available in the summer too after Bayern Munich confirmed on Sunday that he would leave his job with them at the end of the season.
Van Gaal's slow, possession-based game-plan has proved unpopular with fans and with results now taking a downturn - United have also not won in six games - the pressure is increasing.
A Boxing Day trip to Stoke looks another awkward fixture for United and their veteran manager, with Chelsea then coming to Old Trafford on December 28.
Asked what needed to happen for players to recover their draining confidence, Van Gaal said: "To show your professional attitude - that is the only way you can get that back.
"We had done that this week and that is the only way, but now we have to evaluate what we have done here and how we have prepared for this match.
"We shall evaluate what we have done as a staff, and as a team, to make it better against Stoke City.
"And then we have to play within two days against Chelsea. We have to show our professional attitude to improve and to come back into our confidence zone."
The defeat left United fifth in the Barclays Premier League but they had actually started brightly. They controlled the game early on and looked brighter in attack than on previous occasions but they failed to test opposing goalkeeper Declan Rudd.
They were punished by breakaway goals from Cameron Jerome and Alex Tettey either side of half-time and were unable to turn the situation around despite a reply from Anthony Martial.
Juan Mata did force a save from Rudd from a free-kick and Chris Smalling headed wide in injury time but United lacked a cutting edge.
Norwich's game-plan to absorb early pressure and then catch the hosts on the counter-attack, however, worked perfectly. Alex Neil's men then showed commendable discipline to close out victory and lift themselves out of the relegation zone.
It was also a first Canaries win at Old Trafford since 1989 and Neil was sure that would be well appreciated by all connected to the club.
The Scot said: "That is great for the club. I'm delighted for the likes of (majority shareholder) Delia (Smith) and (chief executive) Dave McNally, who put their faith and trust in me. That will mean a lot to them, and to the fans.
"But for me it is just about trying to get as many points as I can for my team. They will certainly take some confidence from that. We have played well in certain games but not got our just rewards. That can be de-motivating and difficult to accept, but I am hoping we will take huge confidence from that and we can grow.
"It is not easy when you are a newly-promoted team and you are fighting against clubs that are far bigger than us. However we showed there is no reason why we cannot win games. We are competitive."