Yogananda said

There is an important ingredient to kriya yoga – awakening Of the shakti. This key ingredient is not talked about.
I have enclosed a page from Devatma shakti

The book is a a wonderful book and would recommend people read it. Many pages of awakening of shakti are there.
The whole process is long but quite delightful to go through
I have enclosed the link for the book
Human ego prevents a disciple from realizing that your following the mechanical process of kriya but the inner awakening – the full force of Awakening is not there It appears but slowly in 3 steps
This entire process can be fast if there is humility, genuine interest in progress and isolation from all for years
Why is isolation needed? It is crucial. The mind is weak and often gets influenced by others. Maya is quick to cast seeds of doubt and many find it difficult to uproot them
However you are only ready for total isolation if your on the right path, able to Live eating less that 1/2 meal a day, have no need for sensual pleasure, always happy without a shred of depression, drink divine nectar daily, and you repeatedly forget you have a body