Intro: The bulk of this was in my response to a post asking what was the big deal with meditation. My answer provides a non-supernatural analysis of the mechanics and benefits of activities such as mediation and prayer. My intent is not to say that there are no supernatural aspects to these things, it was simply to consider the matter without regard to supernatural aspects, whether or not they exist. I also didn't cite anything supporting my assertions simply because they are so numerous and I've got other things I have to do today.

Body: Perhaps the best way to understand meditation, prayer, and like "spiritual" practices to to equate it to exercise.

The body is meant to be used, as is the mind, to stay healthy. Our modern lifestyles often mean that our bodies, and our minds, are not used fully or properly as designed for maximum health. Sometimes we overuse them in certain ways and wear them down. Other times we under use them and atrophy sets in.

When our bodies or minds become damaged through misuse, rest and exercise become great tools to fix the issues. What exercises are best depends on what issues are present and what goals are being pursued.

Focusing only on physical exercise for a moment, a lot of people advocate regular exercise. That might be aerobics, or running, or martial arts or wight lifting, or a combination. Others will also advocate combining exercise regiments in conjunction with diet. But why? What's the point?

One point may just be overall better/optimal health. Longer life through body maintenance, less joint pain through stronger skeletal-musculature health and more capacity to act for the same reason. Perhaps it's just to look better at the beach. Others may exercise simply for the enjoyment of it or the camaraderie they obtain during group activities. Others need improvement in their daily lives, such as police officers or firefighters.

It is very possible that some people exercise to the point that any true functional improvement becomes mute. Wind sprints are great, but if you're not competing does it matter if you knock 2 seconds off your time? At what point point do muscles become nothing more than a fashion statement?

On the other hand, some people have been so weak, so tired and so out of shape, they have no idea that they can feel different, if only they would move. How should they move? It doesn't matter, anything is better than what they are doing and they will see results period if they will just pick something-anything-and stick with it. Other people have always been naturally active but are now facing changes, such as getting your first full time office job. They may actually see a decline if they pick only a low effort, low time exercise regime. Still other people always gravitate towards physical activity in all aspects of their lives, so never really need to undertake a planned exercise regime and might not see any improvement by doing so.

The mind is often much the same as the body and often reacts the same way. If you use it, you develop it. If you don't use it, you don't develop it. If you overuse it without feeding and resting it, it breaks down. It is possible to develop parts of it while letting other parts atrophy or degrade through overuse and under care. And just like the body, there are many aspects to the mind so more than one approach is usually needed to have full mental/physical development.

Education should help develop the mind. We build connections which lead to understanding. There are multiple aspects to these mental skills, language, reason, abstract, visual, temporal, etc. Things such as mathematics and logic are ways to accomplish mental development and strengthening. Philosophy helps us relate to the world and the unknown and order our approach.

Meditation and prayer can be used to develop and impose calmness. It can be used to develop discipline and awareness or even endurance. Studies show the brain is subject to fatigue the same as the body. Just like the body, practice can enhance performance and endurance for the brain.

Just like with exercise, there may be real world needs to address through these methods, but there is also a real benefit just in the basic regimen to maintain aspects of mental health and ability that would otherwise not be adequately addressed without mediation/prayer. What aspects these would be is likely different for every person.

So, what you can achieve by meditation depends on what you need, what you want to achieve and how you go about it. If you've spent your whole life getting up every morning to hit the books on all sorts of subjects followed by making an ordered and detailed plan which you them immediately put into action, you may not get as much as a person whose whole existence up until now has been a strictly physical and impulsive endeavor. Perhaps, meditation can help, but only in certain ways or only by expanding what's already there.

So, the same way that it is wrong to think that exercise means walking into a gym, picking up 20 pound dumbbells and doing 40 curls and being done is the entirety of the exercise spectrum, so is thinking that meditation means sitting down for 10 minutes everyday and repeating "ohm" is the entirety of meditation. If you've never been physical at all, doing the curls will give you significant results. Those results may even be "world changing," by opening up possibilities you never knew existed, but were common knowledge to millions of others. It's the same with meditation.

All that to illustrate, mediation and prayer are ways to exercise the mind. Primarily, they develop the capacity to be self aware of your mental state and exert greater control over it. It also can help with focused thought and clarifying priorities/directions. How well it will do this depends on how well you've already developed those characteristics through other means and how skilled you are at applying meditation/prayer to these goals, or others.

That's why people discuss mediation/prayer, for the same reason people share work out tips, because slight adjustments can mean big results but not everything works the same for everyone.

TL:DR Mediation can be approached much like exercise.