As far as I understand it, praying is just the act of thinking or whispering poetry and/or your own aspirations to yourself structured like requests, so that should be doable in Japanese as well. Let's see...
In my opinion prayer would only act as a distraction from studies. The most productive Japanese study sessions i have are those when my mind is free of any irrelevant thoughts. Some people describe this state of utmost concentration as "being in the zone".
For that sake i find meditation a tool of choice for buffing my study progress.
So basically i would meditate for 15 minutes before my studying session. That "resets" my thoughts and keeps them from wandering.
I also find it very beneficial to meditate after a study, contemplating freshly learned materials, , newly learned vocab and kanji, reflecting on freshly made mistakes.
There are many types of meditation practiced around the globe. For abovementioned purposes Zazen and transcedental meditation work just fine.