1) It is wise to always be upon one's guard when walking alone at night.

2) She remained upon her guard during the negotiation to ensure fair terms.

3) The soldier was trained to be constantly upon his guard in the battlefield.

4) Upon being warned of potential danger, he immediately went upon his guard.

5) She stayed upon her guard as she delved deeper into the mystery.

6) The detective remained upon his guard as he approached the suspect.

7) The security team was constantly upon their guard to prevent any breaches.

8) Knowing the risks, he remained upon his guard and approached the situation cautiously.

9) The villagers were upon their guard, ready to defend their homes against any threat.

10) Upon one's guard, he scanned the room for any suspicious activity.