The Scots have headed to Auckland for their pool decider with England on the back of their 13-12 loss to the Pumas - with Lucas Amorosino scoring the decisive late try in Wellington.
Scotland must now beat England and deny them a bonus point if they are to continue their proud record of reaching the knockout stages of every World Cup.
However Parks claims the loss to Argentina has had a massive impact on the squad.
Parks said: "It's very hard to accept losing that game, but we have to, because it's done. We've got to move on.
"It's the most heart-breaking thing I've been through, rugby-wise.
"Someone asked me about looking forward to England. It's really hard to look beyond this one, but the reality is you have to.
"It's still heavily weighing on the mind.
"The hardest thing to accept is it was on the biggest stage and it was the most important game we've had for a very long time.
"We've had discussions and there is obviously still hope we can still get through."
Despite the agony, Parks insists Scotland can regroup and pull out a result against the auld enemy.
He added: "We are capable of pulling out big results and there's going to be none bigger than this week.
"We've proved we can win games and that (against Argentina) was a game we know we should have won.
"It's a very, very tough thing to take because it was all set up for a big finish. It was just one of those things. It possibly wasn't meant to be."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
$29.99
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.