As someone already pointed, a hymn or verse or mantra motivating for someone might not work for another because of subjective difference. Anyways, some of the popular compositions of Vedanta and spirituality are:
- Nirvana Shatakam by Adi Shankaracharya
मनो बुद्ध्यहंकारचित्तानि नाहम् न च श्रोत्र जिह्वे न च घ्राण नेत्रे न च
व्योम भूमिर् न तेजो न वायु: चिदानन्द रूप: शिवोऽहम् शिवोऽहम् ॥१॥
I am not the mind, the intellect, the ego or the memory, I am not the
ears, the skin, the nose or the eyes, I am not space, not earth, not
fire, water or wind, I am the form of consciousness and bliss, I am
the eternal Shiva...
न मृत्युर् न शंका न मे जातिभेद: पिता नैव मे नैव माता न जन्म न बन्धुर्
न मित्रं गुरुर्नैव शिष्य: चिदानन्द रूप: शिवोऽहम् शिवोऽहम् ॥५॥
I have no fear of death, no caste or creed, I have no father, no
mother, for I was never born, I am not a relative, nor a friend, nor a
teacher nor a student, I am the form of consciousness and bliss, I am
the eternal Shiva...
अहं निर्विकल्पॊ निराकार रूपॊ विभुत्वाच्च सर्वत्र सर्वेन्द्रियाणाम् न
चासंगतं नैव मुक्तिर् न मेय: चिदानन्द रूप: शिवोऽहम् शिवोऽहम् ॥६॥
I am devoid of duality, my form is formlessness, I exist everywhere,
pervading all senses, I am neither attached, neither free nor captive,
I am the form of consciousness and bliss, I am the eternal Shiva...
- Om Purnamadah Purnamidam - Isha Upanishad
ॐ पूर्णमदः पूर्णमिदं पूर्णात्पूर्णमुदच्यते । पूर्णस्य पूर्णमादाय
पूर्णमेवावशिष्यते ॥ ॐ शान्तिः शान्तिः शान्तिः ॥
Meaning: 1: Om, That (Outer World) is Purna (Full with Divine
Consciousness); This (Inner World) is also Purna (Full with Divine
Consciousness); From Purna is manifested Purna (From the Fullness of
Divine Consciousness the World is manifested), 2: Taking Purna from
Purna, Purna indeed remains (Because Divine Consciousness is Non-Dual
and Infinite), 3: Om, Peace, Peace, Peace.
- Om Asato Ma Sadgamaya or Pavamana_Mantra
ॐ असतो मा सद्गमय । तमसो मा ज्योतिर्गमय । मृत्योर्मा अमृतं गमय । ॐ
शान्तिः शान्तिः शान्तिः ॥
1: Om, (O Lord) Keep me not in (the Phenomenal World of) Unreality,
but make me go towards the Reality (of Eternal Self), 2: Keep me not
in (the Ignorant State of) Darkness, but make me go towards the Light
(of Spiritual Knowledge), 3: Keep me not in (the World of) Mortality,
but make me go towards the World of Immortality (of Self-Realization),
4: Om, Peace, Peace, Peace.
- Ek Omkar
Note that most of the popular motivating verses of Vedanta end in 'Om shanti' as they are not talking about environmental peace but the mental peace of mind which is already overloaded with thoughts of world, which a listener should experience after separating real Self from the bondage of mind and world. And once a jiva silences mind, he/she automatically is one with Atman, the source of fearlessness, intelligence, powers and bliss.