It was Lady Macbeth, I think, who told her husband not to lose his courage when he started to doubt their plans to kill King Duncan and seize the Scottish throne.
She simply told him failure was not an option—as long as he had the strength to carry out their fiendish plan.
How Fiorentina could do with her likes right now.
Everything was going swimmingly for the Viola before Christmas, and even outsiders were casting a jealous eye in the direction of the Tuscan capital.
Cesare Prandelli's men had come through a tough Champions League group in some style, they were on target for a top four finish in Serie A, and some of their young starlets were the envy of Italy.
Those times, however, have changed.
The boys in purple sit in the bottom half of the league table, their defence has leaked goals, and their prolific strike force has run dry.
It is not the best state to be heading to Munich for a crunch European tie, especially when your opponents just can't stop winning.
It would be easy to throw in the towel already and accept elimination as the only possible conclusion.
However, that's why Fiorentina desperately needs somebody to make a stand and keep the faith in the football, which got them so many rave reviews earlier this year.
The weekend defeat to Sampdoria did little to raise the spirits.
A wicked deflected headed goal by Franco Semioli (a former Fiorentina player) and a smart finish by Giampaolo Pazzini (also an ex-employee) killed off Alberto Gilardino and company.
It was another crushing blow on a dreadful, dreadful pitch at the Stadio Marassi.
In addition, Mario Santana and Alessandro Gamberini picked up injuries.
The grounds for optimism look few and far between.
But that's exactly why everyone at the Artemio Franchi has to keep their eyes on the goals which they set themselves at the start of the season.
They are still trying to play good football, they still have some top class players, and their manager remains one of the best in the business.
And the easiest way to emerge from this crisis would be a strong result in Germany.
Bayern Munich came from behind to beat Borussia Dortmund on Saturday, but not without throwing the Viola a few crumbs of hope.
The goal they conceded showed some defensive frailty, and there were large gaps which the likes of Stevan Jovetic and Marco Marchionni would love to exploit.
Of course, there was plenty to fear as well.
Fiorentina will need to block up the flanks for Arjen Robben and Franck Ribery and marshal Mario Gomez like they did Fernando Torres.
But it is vital they don't lose confidence in all the things which made them such a hit earlier in the year.
Seba Frey remains an outstanding goalkeeper, Lorenzo De Silvestri is a great marauding full-back, Riccardo Montolivo is having a season worthy of securing a World Cup spot, and Juan Manuel Vargas is simply awesome.
It's not easy to keep your head while people all around you are losing theirs, but that is exactly what the boys from the banks of the River Arno must do.
If they start to waiver and head to the Allianz Arena without the courage they showed in Liverpool or Lyon they will get massacred.
"Nervi saldi", they say in Italy, and it means "keeping your cool".
Fiorentina need that more than ever now. After all, there are still a Champions League quarter-final, the Coppa Italia final, and a decent Serie A finish left to fight for.