Is this line from "Stalker" an allusion to Shakespeare?

Question

In Tarkovsky's Stalker one character states:

Well done, citizen Shakespeare. It’s frightening to go forward; it’s a shame to go back.

This further reminded me of the passage from Hart Crane's Southern Cross:

It is blood to remember; it is fire To stammer back

The translator of the Russian film however might not know the exact Shakespeare quote so might not have translated it to match the Shakespeare quote. Does anyone know what the exact allusion to Shakespeare is? If it is an allusion. For more context the character does on to state:

Therefore, you commanded yourself in a strange voice. You even became sober out of fear.

Doing the obvious Google searches does not yield any answers.

Answer 1

TL;DR: No.

The line from Stalker comes from the English dub of the film. Here’s a bit more context, starting at 19:50 in this YouTube video. Three men, Stalker, Professor and Writer, are approaching an apparently abandoned building in the Zone.

Writer goes slowly towards the building.

VOICE (off screen): Stop! Don’t move!

A cobweb or a translucent cloth falls down at the entrance of the building. Stalker and Professor look towards the building.

STALKER: Why did you?

PROFESSOR: What?

STALKER: Why did you stop him?

PROFESSOR: What? I thought it was you.

Writer stands still for a moment, then hurries back.

WRITER: What happened? Why did you stop me?

STALKER: I didn’t stop you.

WRITER (to Professor): You? (Professor shakes his head.) Damn it!

PROFESSOR: Well done, citizen Shakespeare. It’s frightening to go forward; it’s a shame to go back. Therefore, you commanded yourself in a strange voice. You even became sober out of fear.

In context, Professor is not quoting from Shakespeare, but rather using “citizen Shakespeare” as an ironic or mocking form of address for Writer, who, as the film makes clear early on, is no Shakespeare, but rather a drunk who has lost his inspiration and hopes to get it back in the Zone. When Professor says, “It’s frightening to go forward; it’s a shame to go back,” this is a literal description of the events that just took place.

Answer 2

The words "It’s frightening to go forward; it’s a shame to go back." are possibly an allusion to some of Macbeth's lines near the end of Macbeth, act 3, scene 4 (emphasis mine;):

(…). for now I am bent to know,
By the worst means, the worst. For mine own good,
All causes shall give way: I am in blood
Stepp'd in so far that, should I wade no more,
Returning were as tedious as go o'er:
(…)

Macbeth's way forward will involve bloodshed, but if he went back, all would be for nothing, as he had said earlier when thinking about the weird sisters' prophecy again and how the murder of Duncan may have been for nothing (Act 3, scene 1):

For Banquo's issue have I filed my mind;
For them the gracious Duncan have I murder'd;
Put rancours in the vessel of my peace
Only for them; and mine eternal jewel
Given to the common enemy of man,
To make them kings, (…)

For this reason, it would be "a shame to go back" in the context of the wading metaphor from the first quote.