One's bones becoming ground to dust is a fitting description. That's a graphic image. Imagine your body, flesh and bones going through a mincer... Ready for that? That is what sadhana, committed practice, does. Bumps, emotional upheaval, are inevitable and actually purposeful. Every time that happens, it reminds us about our motivation and commitment, as well as forces us to practice and master our practices. Will we get scared and run away because of some bumps? Too scary? Too hard? How well do we really know that we are confused? How much do we want it to end? It all boils down to simple questions and if you know how to answer them, the path becomes much much easier. Those who are uncertain, bitch and moan because their view of the path is lopsided or wrong. Some want to be happy but the thing is that lasting happiness comes only through great yogic hardship and if there is no willingness to experience that, it'll just be unpleasant and uncomfortable.
When the going gets tough, a real practitioner, clenches her or his fists and remembers the suffering of all sentient beings. If you look at tantric imagery, you can see many yoginis, yogis and deities not looking serene and peaceful. This is because at times yoginis and yogis need to be warriors and merely being peaceful, happy and serene just won't get the job done. One will find happiness and serenity, become a peaceful buddha, after the deadly poisons of the mind are removed but until then, better learn to fight!
In Finnish, we have a saying that "our blood is measured" through hardship. Yogic hardship, i.e. dark nights, make us mature in two ways: they release karma and kleshas but also make us mature as individuals so we develop our character. Advanced adepts have character to them. Yoginis and yogis are not sissies or bullshitters because proper practice shatters all that. When yoginis and yogis laugh, gods attain liberation and demons run away in horror!