Sri Aurobindo
Letters of Sri Aurobindo
Volume III - Part 1
Fragment ID: 12168
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.
nature was capable of has been done and that would mean it was not capable of much.