In Jain Dharma, the main sacred (powerful) mantra is:

1. Navkar (Namokar) Mahamantra

Original Prakrit text (common to both Digambar & Shwetambar):

ṇamo arihantāṇaṁ ṇamo siddhāṇaṁ ṇamo āyariyāṇaṁ ṇamo uvajjhāyāṇaṁ ṇamo loe savva-sāhūṇaṁ

eso pañca namokkāro savva-pāvappaṇāsano maṅgalāṇaṁ ca savvesiṁ paḍhamaṁ havai maṅgalaṁ ( jainknowledge.com)

Simple meaning (arth):

• Namo Arihantāṇaṁ – I bow to the Arihants (perfect beings who have destroyed inner passions and still have a body).
• Namo Siddhāṇaṁ – I bow to the Siddhas (liberated souls, without body, in moksha).
• Namo Āyariyāṇaṁ – I bow to the Āchāryas (heads of the Jain order, guardians of discipline).
• Namo Uvajjhāyāṇaṁ – I bow to the Upādhyāyas (spiritual teachers of scriptures).
• Namo Loe Savva‑Sāhūṇaṁ – I bow to all Sādhus and Sādhvīs (monks and nuns) in the whole universe.
• Eso pañca namokkāro – These five bowings,
• Savva‑pāvappaṇāsano – destroy all sinful karmas,
• Maṅgalāṇaṁ ca savvesiṁ – among all auspicious things,
• Paḍhamaṁ havai maṅgalaṁ – this is the foremost auspicious. ( jainknowledge.com)

Why this mantra is used when you feel scared

• It does not ask for miracles or worldly protection.
• It turns the mind toward the purest souls and their qualities.
• By remembering them, fear, anger, and attachment slowly reduce, karmic bondage becomes lighter, and the mind becomes peaceful and strong from inside. ( jainknowledge.com)

So, when you feel afraid:

1. Sit or stand quietly.
2. Take a few slow breaths.
3. Chant Navkar Mantra softly or in your mind, 9, 27, or 108 times, trying to feel its meaning.
4. Think: “I bow to those who have no fear at all; may such fearlessness arise in me also.”

Both Digambar and Shwetambar accept this mantra fully; only small pronunciation differences exist. The meaning and spiritual essence are the same. ( jainknowledge.com)

You can read more about the Navkar Mantra and its benefits here and a simple concept explanation here .