How does LoA actually work?

People say "what you believe will manifest" but why does the opposite always seem to manifest instead? How can you be sure? Every time I believe or want to give power to the positive yet remain aware of risks when an opportunity presents itself, the negative manifests instead? Am I not focusing hard enough? Does law of attraction require blind belief? Is spirituality similar brainwash to religion when it comes to believing in anything - because it really starts feeling like it. Does it require you pull lies over your truth or bend the way you really see things, so you can start believing the good stuff will happen? Or do I have to be more willful and persistent with manifesting my own truth? Can't the universe even mirror enough, so I could actually see where I'm going wrong instead of having to ask out loud and therefore compromise the manifestation to more dirt and lies, which are a risk?