I gave an advice to my friend who is doing a startup. I told him it probably won't work out. But we continue with our own line of thinking because the outcome totally depends on reality. Also, my friend can tack on lot of ifs later on (if only this and this and this had happened, I would be successful) to "prove" himself right. It might be possible that with no decisive outcome favoured by reality, we would both continue to be right in our heads.