Hi guys. I think i'd echo Blink's comment. Perhaps the issue is basically that the Grace/intuition/knowing/access to the true nature of mind that brings higher consciousness/loving behaviours/wisdom/genuine intuitive knowings comes in on a very low strength signal.
One which gets drowned out against the babble of compulsive egotistical thought that fills most of our heads pretty much all of the time.
It's said that meditation/monastic life/retreats/isolation in caves or whatever/darkness potentially play at several levels to help us to receive this signal.
In normal life we're continuously faced with the need to respond to our environment, and these responses are inevitably driven by selfishness. That's not a judgement, just a statement of the inevitability of the fact that we cannot normally by act of discursive intellect/thinking mind somehow magically decide to make decisions which transcend/place us outside of the whole logical framework on which the very perception of self that allows such thought is built.
You can't for example quiet your thinking mind by direct application of willpower. Any more than you can directly apply willpower to the act of 'not thinking'.
This is the mechanism that (normally, see below) no matter how unhappy we become keeps us trapped in this self reinforcing reality. Samsara in Buddhist terms.
This inevitably means that the most available way for most of us to tune into the low volume higher knowings above is by placing ourselves in conditions where ego thought are slowed, and eventually stilled.
The alternative (as enlightenment experience) seems to happen spontaneously in only a very few (e.g. Eckhardt Tolle) - life seen through the egotistical lens becomes painful enough to trigger some sort of rejection of this way of seeing - a reboot of consciousness. Once we make this break it seems we no longer perceive through the filter of ego view and so can not be taken in by it again. Trouble is most of these seem to have first served their time on the 'slow' road'.
The theory is that the various methods listed above help create circumstances that make the gradual stilling easier. Monastic life eliminates most of the need to worry about life issues and removes most external stimuli. (unless you happen to be a Burmese Buddhist monk

) Meditation is effectively the practice of not doing, and more importantly of not thinking. Mind settles slowly over time, even when meditating. So more extended periods of meditation as in retreats and isolation allow for further settling. Extended retreats in darkness are I guess the ultimate in bringing together of all the factors.
The above booklet proposes a biochemical framework that underpins this shutting down.
What's the reality of this? I'm not sure. My experience is that a week's meditation retreat definitely produces a stilling that develops all week - there seems no reason why it should not continue. This stillness carries for some weeks after the retreat, and in fact seems to produce some sort of real ongoing change in the individual. Tibetan Buddhism regards multi year retreats as an essential part of spiritual development - albeit only when one reaches a defined stage of development.
I don't know for sure, but it's probably a dynamic process. When for example we indulge the sub personalities in our ego (the pain body/victim, the bully, greed for wealth/power whatever), especially when we do this intensively we pour energy into and build ego in a manner which presumably can reverse the benefit of whatever meditation and other spiritual work we do.
We drive ourselves deeper into Samasara and cut ourselves off from the Grace/love/higher mind that's necessary for happiness...
Yet another reason why lightness, openness and spaciousness of view are such an important part of the spiritual life......