हृदये जन्मान्तरमहस्रेषु भावनायोगात् तस्मात् दुर्धरः ।'क्लेशोऽधिकतरस्तेषामव्यक्तासक्तचेतसाम् ।अव्यक्ता हि गतिर्दुःखं देहवद्भिरवाप्यते' इति भगवद्वचनात् ।न आन्तरैः रागादिभिर्वाह्यैरपि दानवादिभिः शत्रुभिः पराजित इति अपराजितः ॥
In plain words
He is held in the heart only through the discipline of contemplation, kept up across thousands of births — and so He is Durdhara, hard to hold. The Lord himself says: "The strain is greater for those whose minds are fastened on the unmanifest; for the unmanifest goal is reached only with difficulty by people who carry bodies." And no enemy defeats Him — not the ones within, desire and its kin, nor even the ones outside, the dānavas and their sort. So He is Aparājita, the undefeated.
Close to the Sanskrit
Because of the practice of contemplation in the heart over thousands of successive births — therefore, Durdhara, hard to hold. From the Lord's statement: 'Greater is the affliction of those whose minds are fastened on the unmanifest; for the unmanifest goal is reached with difficulty by those who possess bodies.' Not defeated by inner enemies such as passion, nor even by outer ones such as the dānavas — thus, Aparājita, the undefeated.