As devotees, we should know our limits of spiritual purity. We should not imitate pure devotees in terms of eating, sleeping and other mundane bodily functions. Srila Prabhupada enforced minimum rules such as four regulative principles, chanting 16 rounds and honoring prasadam. If we practice this sincerely and diligently, we can advance towards Krishna. But out of false-pride and duplicitous nature, if we make a show of advancement of sleeping irregular hours, eating little, engaging in bhajana etc, then such show will eventually pull us down. Therefore we have to be humble in progressing towards Krishna.
What does that mean?
It means we have to wait till Krishna allows us to get to the next level of purity whatever it may be. We have to perform to our current capacity with sincere diligence and wait for Krishna to give us confidence within us to go to the next level. Either that or we advance purely based on our attachment to our Guru. This is not so common. Intense attachment to Guru can enable one to disband material hankerings instantly and take up to deep levels of Krishna consciousness.
However, those who are not at that level of attachment can however practice vaidhi bhakti gradually till they receive higher taste from Krishna and in that way progress towards spontaneous bhakti. But for all of this to happen, we have to acknowledge our insignificant nature, and in that mood practice our sadhana (whatever we have committed to) strictly every day and beg for Krishna’s mercy to make progress towards Him.
Patience, confidence and enthusiasm is the key.