This question tests your understanding of verb patterns after "let" in the passive voice. The sentence structure is: "Don't let yourself _____ by your failure."

The key is to identify the correct form of the verb "depress" that should follow "let yourself." The word "let" is a special verb that is followed by an object and then the base form of another verb (the bare infinitive). However, in this sentence, the meaning is passive because "yourself" is the one being affected (you are being depressed by your failure).

To form the passive voice after "let," we use the structure: let + object + be + past participle.

Therefore, the correct phrase to fill in the blank is "be depressed."

Step-by-Step Reasoning:

Step 1: Identify the main verb. The main verb is "let."

Step 2: Identify the object. The object is "yourself."

Step 3: Determine the voice. The meaning is passive (yourself is depressed by something).

Step 4: Apply the rule for the passive form after "let": use "be" + past participle.

Step 5: The past participle of "depress" is "depressed."

Final Answer: The correct choice is "be depressed." The complete sentence is: "Don't let yourself be depressed by your failure."

Why the other options are wrong:

"being depressed": "Let" is not followed by a gerund (-ing form).

"depress": This is the base form, but it would create an active voice sentence (e.g., "Don't let yourself depress others"), which doesn't fit the meaning here.

"to be depressed": "Let" is not followed by a "to-infinitive." The correct structure uses the bare infinitive "be," not "to be."

Related Topic: Verb Patterns

Some verbs, known as causative verbs (like let, make, have), have specific rules for what form of verb follows them. "Let" and "make" are followed by an object and then the base form of a verb (e.g., "She let him go"). For the passive voice, the structure changes to "let + object + be + past participle."

Related Formulae/Rules:

Active Voice: let + object + base verb
Example: I let my brother use my car.

Passive Voice: let + object + be + past participle
Example: Don't let the opportunity be wasted.