Here is a set of practical strategies that do no harm, only defend yourself, and specifically leverage human weaknesses to protect yourself.

1. Exploit people's "Desire to Save Face" — Less confrontation, more boundaries

Human nature: Everyone fears losing face, feeling embarrassed, or being publicly humiliated.
Usage:
Avoid direct confrontation or burning bridges; instead, set rules gently but firmly.
The other person, for face reasons, won't push you too far.
Core: Give enough face, maintain your bottom line.

2. Exploit people's "Seeking Benefits and Avoiding Harm" — Don't give everything easily

Human nature: When things are too easy to get, people don't cherish them; the more you give, the harder it is to leave.
Usage:
Be kind to everyone but keep some for yourself.
Don’t reveal your full sincerity all at once; respect will follow.
Core: Your kindness must be scarce to be valuable.

3. Exploit people's "Admiring Strength and Fearing Weakness" — Appear steady, be tough inside

Human nature: The softer you are, the more others will test you; the more stable you seem, the more polite they are.
Usage:
Complaints, playing the victim, or exposing vulnerability should be minimal.
Speak less, stay calm emotionally, and maintain a neutral attitude — this is the best armor.
Core: Calmness commands respect; it’s more effective than aggression.

4. Exploit people's "Holding Grudges but Forgetting Kindness" — Help others with boundaries

Human nature: Help ten times, but if you refuse once, they become enemies; help less often, but occasionally help, and they become grateful.
Usage:
Help just enough; don’t take full responsibility or commitments.
Be kind but with a sharp edge.
Core: Kindness must have limits; otherwise, it’s weakness.

5. Exploit people's "Conformity and Fear of Being Different" — Less explanation

Human nature: Most people only believe what they want to believe and ignore reason.
Usage:
When misunderstood, don’t over-explain.
The more you explain, the more they think you’re guilty.
Core: Act righteously, speak less, and be more powerful.

6. Exploit people's "Greed for Small Benefits" — Small favors for peace, firm stance on big issues

Human nature: A small benefit can resolve many conflicts.
Usage:
For trivial matters, give a little, show some face.
On principles, money, or emotional boundaries, don’t give an inch.
Core: Small gains for peace; big gains for life and death.

7. Exploit people's "Easily Influenced by Emotions" — Keep your emotions in check first

Human nature: When angry or anxious, it’s easy to reveal flaws and be manipulated.
Usage:
When the other is anxious, stay calm; when they cause trouble, don’t get upset.
Your calmness will leave them helpless.
Core: Whoever loses control first, loses.

A final, ruthless self-protection logic:

Understanding human nature isn’t for manipulating others, but to know in advance how others will act toward you, so you can preemptively defend yourself, stay composed, and avoid injury, internal conflict, or being manipulated.