Should we be spiritually engaged at all times and in all situations? Or stick to a schedule?

From the classical and Medieval eras, during which Christianity was established, the ideal was an overall religious basis for society, with a religiously approved monarch - but in practice life was divided between religious and secular activities.

In essence; there was a prescribed (minimum) ritual and ceremonial religious life; and the rest of a personal and community time was de facto engaged in all the other necessities of living. The proportions of secular and sacred varied, but the division was necessarily present (in practice) even in monasteries. 

This division was also (usually) reflected in terms of individual subjective experience. In general, people strove, and were perhaps often able, to achieve a properly spiritual, devotional attitude during daily prayer and formal church services and the like; but accepted that this level was impossible to sustain.

And indeed, from whatever combination of character and circumstances, it was often impossible to be spiritual at all. The main thing was to "do it" in the prescribed times and places. 

Indeed, as the centuries passed, it seems that even the minimum frequency of experienced religious participation was increasingly difficult to achieve. People could conform to all requirements in "the letter", yet "the spirit" became feebler...

More and more often, "the spirit" was altogether absent. 

Against this backdrop of enfeebled faith and increasing apostasy; were those (from the late 1700s, but much more so later) who advocated (and sometimes claimed to achieve) a continuous and unbroken spiritual life. 

They claimed, indeed, to strive for what they saw as the real possibility of living all life (from waking to sleeping, and ultimately even during sleep) in a state of devotion, spiritual awareness, religion. Conversely, they poured scorn on the ideal and reality of "Sunday Christians" - who switched-off religion, in between their required church attendances. 

Such people included Christian revivalists of various kinds  - and often these claimants were not Christian. Often enough they were atheists (spiritual but not religious), or neo-pagans of a wide range of types. For instance a serious Buddhist told me that a Zen Masters' whole life was one of continual spirituality, even when doing the most routing chores. More generally, it was claimed that this could happen by the continuous and habitual effect of prayer (i.e. a "mantra": this is also one of the expressed ideals of the Jesus Prayer.) 

As of now, in The West, these two religious ideals still dominate:

On the one hand, a Medievally-rooted ideal that aims at serious spiritual participation in relation to a finite series of discrete and pre-specified practices, times, and places; usually of a formal and prescribed nature. 

And, on the other hand, an ideal of qualitative "enlightenment": the idea that a person can break-through to a permanently transformed nature; a life that is always and everywhere spiritual. 

My belief is that neither of these ideals actually work - for different reasons...

But that they don't work just seems a fact of observation. 

Therefore we ought to seek for something that does work. 

We need another ideal for our spiritual life. 

One might be that we try various possibilities, and do more of whatever works for us... Meanwhile monitoring the situation for how things are progressing (with an awareness that any activity or plan may do us - personally - harm, as well as perhaps good). 

Another notion is that we strive for a higher self-awareness, and by this aim to recognize and "seize the moment" for spiritual activities - not to put them off. 

And also we might strive to hold-onto the insight that - whatever we do in this mortal life - it cannot be sufficient; because this mortal life is not, and is not intended to be, The Whole Thing. 

If we are (as I believe) eternal Beings, then we lived (as spirits, IMO) before this incarnated mortality; and also we will continue to exist (in some form, about which we have a choice) after we die mortally. 

This life is therefore a finite phase between eternities. 

Therefore, instead of deluding ourselves that there is any possibility at all of an ideal life during this mortality; our best bet is to regard our task as trying to have the right kind of helpful experiences; and learning the right kind of lessons from whatever actual experiences come our way. 

This mortal life is intended to be transformative; but the intended (and perhaps, in significant ways although not completely,  achieved) transformation is not for this mortal life; nor is eternal qualitative spiritual transformation even possible in this world of change, of entropy and death. 

Therefore, as with any kind of intentional development, such as the following analogy of school or college work; we may realize that:

On the one hand that we cannot always be studying and practicing. And if we seriously attempt this, we will not only be wasting our time - but indeed sabotaging the possibility of that focused and intense (therefore necessarily brief) learning which really works. 

And, on the other hand; that one secret of effective learning is to be aware of any moments when the opportunity for some really special experience has arrived. 

When that moment is here; we should be able to set-aside the routines, plans and programs devised to get us through dull-dry times; and, seizing the opportunity, take the chance, here-and-now.

And learn from it that which is divinely-intended for our benefit. 

If at all possible.