I found this quotation recently in the 13th century Japanese text, the Essays in Idleness, and have been giving it some thought:
Someone asked the holy priest Honen how to prevent himself from being negligent in his practice by inadvertently nodding off when chanting the nenbutsu. “Chant for as long as you stay awake,” answered Honen. Venerable spoken.
Translation by Meredith McKinney
I like this approach wherein Honen is encouraging a “do your best” with respect to Buddhist practice vs. “do a set amount” that you often see in modern Buddhist literature. For folks who dabble in Buddhism or spiritual practices in general, in particular meditation, it’s often the case we treat it as a prescriptive thing. A teacher prescribes a specific thing (do X for 15 minutes), and we try to do it. It works for a bit, then life gets in the way, and we’re forced to make awkward choices.
Well, life tends to mitigate against complete commitment, doesn’t it?
Count Saint Germain, Castlevania animated series, season 4
If you are a parent, this goes double. You might wake up early, and have a few minutes to get some “personal time”, but if you’re exhausted and your brain is fried, you might not be able to muster the energy for any spiritual practice. If your kids were up late last night, and you wake up late, you don’t even have the benefit of personal time. If you’re working extra hours that day, parent or not, you might not know when you’re done, or have to sacrifice personal time to keep your job.
All this makes consistent, prescriptive spiritual practices unrealistic for most people, but it’s important not to give up either. Hence Honen’s advice makes a lot of sense.
Gleanings in Buddha-Fields 