It’s hard to know what effects praying might have on the external world. Does it have any effect?
But we should easily conclude a great effect of praying starts by changing our world from within.
An example of this is praying for people that you may feel have treated you wrong or are your ‘enemies’.
If you pray for their well-being it can change you. It may be a hard thing to do. We often feel like others are bad people and are against us. Reality is we are all flawed people and for the most part believe we are good or that we are the ‘good guys’.
By praying for ‘enemies’ it forces us to see them as with us and not against us. It gives us empathy towards their situation. It takes away our anger and gives us pause.
You may not think your prayers can move mountains, but it can change you. That change inside you can help change how you act towards others and thus changes the world.