It occurred to me after finishing this post that perhaps the individuals in question believe that affirmations actually change objective reality, as opposed to one’s attitude. It seems that there are people who believe this.
In my view, though, this is to confuse wishful thinking with prayer. Prayer—I’m speaking particularly of prayer of supplication—isn’t simply a matter of warm positive thoughts, prayed with intensity, as though I can will something to happen without taking concrete action. Prayer is matter of asking another person for help, and especially a person in a position to take the concrete action required. When I ask Jane to pick something up at the store for me, there’s a sense in which I’m praying her to do that. And when I ask God to bless someone, or to help them through some trial, or to help me through some trial, I’m not simply wishing that outcome; I’m asking someone in a position to do something. According to Catholic theology, God is the creator of everything other than Himself, the first cause and final end of everything that is, and the one who keeps the whole shebang running. It’s His universe; we just live in it. And we have reason to believe, because of Christ’s death and resurrection for our sake, that He loves us and cares about what happens to us.
And of course, just because I want something desperately and pray for it steadfastly, I won’t necessarily get it; any more than my mother would have let me play with the hot iron when I was a toddler.
Wishful thinking, on the other hand, might change your attitude; but it can’t change what is.