Redknapp admits last weekend's 1-1 draw with Wigan was hard to take, the Latics snatching a point in the final seconds after QPR had overcome the sending-off of Bobby Zamora to take a well-deserved lead.
That result left QPR seven points adrift of 17th placed Sunderland with six games remaining, the first of which comes at Everton on Saturday afternoon.
Redknapp said: "It was disappointing - a big blow for us. We worked so hard to get in front with 10 men.
"It wasn't easy, but you've got to get on with it. There's still some life left in us. We've got to go again now.
"It's going to be hard (staying up), but while there's still a chance, you've got to keep believing.
"Saturday is massive. We need to win four games and draw one to give ourselves a chance. There's not many tougher places to go than Everton. They're a good side - a proper football club."
Redknapp admits Zamora's suspension will make their job harder, adding: "Bobby's sending off was a rash decision and missing him for three games is a big loss.
"It was a crazy challenge and it's cost us dearly because we lost him for most of that game and for the next three matches. He should be disappointed. He's not 100% fit, you can see that, but he's still a good player.
"When Bobby and (Loic) Remy have played together we always look like we're going to win, but we can't get the partnership together.
"Often one of them has been injured and now Bobby's suspended. This has cost us dearly. Remy's our joint leading goalscorer now with five goals. That's been the problem here - we've had no one to score goals. How can you have a leading goal scorer who's only scored five goals? It's almost impossible."