My mum believes in all of this. It's supposed to be that if you're focusing on negative things all the time (I'm so lonely, I never meet anybody, I'm so skint, etc etc) then it attracts more of that negative stuff whereas repeating an affirmation in your head instead (Money flows freely to me, I am financially secure, I am an attractive and worthwhile person, etc etc) to counter these negative thoughts then it's supposed to attract the good stuff to you. But you have to use the affirmation as though it is already true, because thinking "I want a bigger house, I want my children to stop being so rude, I want a better job" then the universe will keep you wanting.
It's an interesting way of looking at the idea of positive thinking, but just be careful you don't get too caught up in it. I used to get really anxious because I would imagine horrible things happening to me or DS and then worry that because I had thought it, I was making it more likely to happen and I would lie awake whispering "I am safe, we are safe, we are ALL safe, the house is safe." in order to "protect" us from the bad thoughts. One day I realised that it doesn't matter. Most people who have house fires or, god forbid, horrible accidents happen to their DC haven't thought about it at all, and lots of people who worry about it constantly are fine. So it probably has no effect at all. I do still do the "We are safe" thing but I only do it once now. I don't repeat it inside my head for hours. It's just, we are safe. We have a smoke alarm, I have my phone, I know the escape routes. Everything is fine. And that's it.
I do think the positive thinking about money etc seems to work because it works for me! But perhaps it's just that when you're focusing on attracting money you notice every unexpected bonus that comes your way whereas normally you'd take it for granted.