Kriya is great if done like instructed
The source is spiritual commentary by Shyam Charan Lahiri. It has 3 volumes It is a collection of letters and commentary by Lahiri Mahasaya – things that he constantly talked About. This was from a letter he wrote to a disciple. Beyond that I can give no authenticity
The letter basically states one must do kriya properly and whole heartedly with full attention within. If the mind wanders on worldly matters and is not done with attention to chakra that will not help
Full devotion to Guru and going within is needed
It is a cautionary remark that Lahiri Mahasaya made that do not do kriya mechanically
There are other letters and commentary
I have no attachment to any publication.
I wish everyone success and much love on your path.
My apologies for hurting your feelings
Bhavin