Gita : Ch-12. Slo-5. Discussion-5.

Srimad Bhagavad-Gita :
  Chapter-12. ( Bhakti-yogam)
  Slokam - 5. (For those whose minds are attached to the unmanifested, impersonal feature of the Supreme, advancement is very troublesome. To make progrese in that discipline is always difficult for those who are embodied.)

Discussion - 5.

Whosoever devotes themselves to contemplation of the atma will certainly prapnuvanti or attain the Supreme Lord which means that by realisation of the atma is essentially realising an essence of the Supreme Lord which is like unto His essence as paramatma the Supreme Soul within the etheric heart of all living entities.

This is what is affirmed later in chapter 14, slokam 2 with the words mama sadharmyam agatah meaning endowed with a form similar to the Supreme Lords.

The Mundaka Upanisad III.I,II,III beginning niranjanah paramam samyam states :-
Absolved from all sins one achieves sublime similarity with the Supreme Lord.

Also in Mundaka Upanisad I.I-V beginning atha para yaya tad aksharam adhigamyate which means : -
Now that the higher science by which the akshara can be reached.

Parabrahma or the Supreme Lord Himself is also designated by the word aksara for He is the source of all beings.
That the Supreme Lord is known as Parabrahma is confirmed as distinct from the atma will be explained later in chapter 15, slokam 17.

But those who minds are attracted to avyakta the unmanifest, impersonal brahman, their tribulations and difficulties are great.
This includes those who meditate upon the atma as well for the meditation of controlling the mind to think of all activities in relation to one's individual atma without being able to imagine it in any way while performing physical and material activities is tantamount to great struggle and futile results.

To be continued  ...