When the mind consciousness has no clue how to think about a problem, and even focused thinking feels very exhausting, what should one do at such a time?
Just let the mind consciousness package and condense the problem, then hand it over to the manas, letting the manas carry this problem at all times and deliberate (manasikāra) upon it, while the mind consciousness does whatever it needs to do. One can do some light activities, such as moving the body, tidying clothes, cleaning up, and so on, trying not to think about other things, so as to avoid drawing too much of the manas' attention away, which would distract the manas too much and prevent it from deliberating on the main problem.
During these light activities, although the manas is also somewhat distracted, it still devotes part of its energy to considering the problem. If the activities are too many or too great, the manas will be too distracted and unable to consider the main problem. When the manas becomes especially interested in this problem and wants to solve it, it may continue deliberating during sleep, and perhaps dreams will appear, in which it pulls the solitary consciousness (mano-vijñāna-eka-citta) along to think and investigate together, while still being able to sleep. This is the best and most effortless way—the mind consciousness does not feel tired.
If the mind consciousness is not afraid of getting tired, it should also focus on pondering this problem during the day, working together with the manas to overcome the difficulty. This is the fastest method. If the mind consciousness, fearing fatigue, does not participate in the thinking, then once the manas has worked out a rough line of thought, the mind consciousness will still be needed to deliberate in detail, and it must still work together with the manas to solve the problem. But one overall principle is that the manas must definitely participate; if the manas does not participate, the problem cannot be solved.
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