It's turtles all the way down. *chuckles*
I think, 'manifesting,' as I know it, to be called, translated from, 'new age,' to, 'Christian,' is prayer.
Whether you are asking God/Jesus/Universe/Higher Power/Great Big Turtle, I think it's fine to ask, nothing wrong with that, perhaps even brave to do so sometimes.
But, for me, having a decent grasp of chaos theory, it's easy to see why a lot of prayers wouldn't be answered.
If 1 Million people all prayed to win the lottery and won, that million dollar jack pot would be worth 1 dollar for each of them (and make a bit of a joke of the known laws of physics).
Now take that example and extrapolate it, to nearly anything you can think about.
Let's say my mother has cancer, and I ask Big Daddy upstairs, to save her. Well, perhaps if she goes into remission for 7 years, in the 5th year, in December, she will step on a cricket that happened to be the neighbor's boy's pet. He goes inside and starts crying and having a fit. The neighbor is on an important phone call for business, and fails to make an important sale that day because the prospective client just doesn't really like kids, is a rich prick, and was already having a bad day.
The father is a good man though, and eats it just fine; however, the business's stock loses a few points. So a few months from then, after the next quarterly earnings report, some one has to get laid off. That person, just happened to be, a nice young woman who was saving to pay her way through a nursing degree program. As it turns out, she really needed that job, it paid really well; but, now she is forced to go work at a walmart, till something better comes along.
However nothing better does come along; and she never ends up becoming a nurse. If Big Daddy hadn't intervened to put my mother's cancer in remission, that woman, would have not only became a nurse, but found that her true calling was to become a doctor; she would have gone on to pursue a doctorate and become a leading cancer specialist, and would have saved countless numbers of new lives with research done during her doctoral thesis.
So, in my opinion, Big Daddy, has things to think about, when entertaining the wishes of mere mortals.
For me, I pray. I ask for things, very cautiously, timidly, fearfully, and am quite uncertain when doing so. I pray for others some times too; but, less and less these days (unfortunately). I ask, I petition The Universe.
I say, "If it be possible and not too much trouble, or more trouble than it'd be worth, let X be so." Or, "If it be possible and a benefit to all beings, let X be so." I used to do that with a lot of faith. However, one time my, 'wish,' really was granted, exactingly so, a year or so later, with quite devastating and also quite wondrous consequences. Ever since then, I have a lot of trepidation about petitioning. I do try to keep others in my thoughts too and petition for them, wish them well, pray, etc.. Seems less risky to wish nice things for others, heh.
I once prayed for a buddy of mine to get a lap dance when he went to visit his sister at college; and hot damn, he got one! lol. I was so happy about that. Was that the power of prayer? Or was that the power of college dorm rooms?
I think, though, ultimately, manifesting, petitioning, prayer, etc.. is at best, an exercise in cultivating compassion, hope, patience, faith, and courage.
I think it's fine to send an S.O.S. to the world, the universe, etc..
However...
"Be careful what you wish for, you might just get it!"
Also, if you are hungry. Don't pray for a sammich, get up and go make one!