If you are too trusting of the invisible then you buy an e-book for £50 that promises to make you an overnight millionaire. So the trick is to discern the invisible stuff that's true from the invisible stuff that's a trick otherwise you're helpless in a world where just about every decision you make has to do with things that are invisible. The best advice is to be skeptical. Test and measure and do your research (seeing if the thing is the truth is often a useful starting point to help you move forward). The truth can't be a relative concept, it's just so often invisible.