What does it practically mean to fix one’s mind on Krishna?

The following is an excerpt from a samvaad (dialogue) session with Acharya Prashant.

मय्यावेश्य मनो ये मां नित्ययुक्ता उपासते ।

श्रद्धया परयोपेतास्ते मे युक्ततमा मता: ।। 12.2 ।।

mayy āveśhya mano ye māṁ nitya-yuktā upāsate

śhraddhayā parayopetās te me yuktatamā matāḥ

The Blessed Lord said: Those who, fixing their mind on Me, worship Me, ever-steadfast, and endowed with supreme Sraddha, they, in My opinion, are the best versed in Yoga.

~ Shrimad Bhagavad Gita, Chapter 12, Verse 2

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क्लेशोऽधिकतरस्तेषामव्यक्तासक्तचेतसाम् ।

अव्यक्ता हि गतिर्दु:खं देहवद्भिरवाप्यते ।। 12.5 ।।

kleśho ’dhikataras teṣhām avyaktāsakta-chetasām

avyaktā hi gatir duḥkhaṁ dehavadbhir avāpyate

Greater is their…