Why am I not aware of the process of assimilation?
Hardly one ever feels that. It goes on under cover.
The period of assimilation can either be a perfect quietude or else the assimilation can go on behind the veil, as it were.
The difficulty is that I am not conscious of the assimilation taking place. It almost seems a cessation of sadhana.
Quite natural. But one must keep in the inner being the faith and knowledge that it is an assimilation and not a cessation, even if it looks like a cessation.
If I could only watch this process behind the veil, all the wrong reactions of the assimilation would cease.
How on earth could it be said then to be behind the veil? It would be a very unveiling veil.
During these periods the experiences etc. come like mere flashes or glimpses and disappear in a short time. During other periods they come almost like a state, as a normal thing to the inner being.
That is as it should be.
Do I still need long periods of assimilation?
The periods of assimilation continue really till all that has to be done is fundamentally done. Only they have a different character in the later stages of sadhana. If they cease altogether at an early stage (you are still in a very early stage), it is because all the nature was capable of has been done and that would mean it was not capable of much.
The only change in the assimilation periods afterwards is that certain things remain settled while the assimilation applies to others that are not yet settled in the system. E.g. one feels always a constant peace in the inner being, but disturbances go on on the surface, till the surface also has assimilated peace. Or perhaps peace is settled everywhere and always there, but knowledge comes and goes, or strength comes and goes. Or all these are there but Ananda comes and goes, etc. etc.
If they stop early, it means that all has been done that could be done and nothing more is possible; the later and more advanced developments of the sadhana are not possible, — if they were, the assimilation periods would continue until all was developed and not cease. The only reason for such a premature end of the sadhana would be that the sadhak is not capable of going farther.