This mindset doesn't make so much sense to me when the end product balls down to making profits for oneself, yes the rich stake up huge amounts to get something bigger and the poor in the other hand is fighting for their financial freedom in that same vein but putting all of that aside a good trading mindset is what matters which involves knowing the right way to trade and all of that.
Good mindset is the priority for all traders, without a good mindset, you're defeated already and all your decisions will be heading towards you losing. There isn't any means which a trader that isn't optimistic about the trade they're about to take is going to be able to analyse the market accurately to get a good trade firm it. When this happens is merely luck and not because if the smartness of the trader. Trading mindset has alot of things attached to it like your frequent analysis to be done on the market to make sure you're capable of being a good trader. Being rich shouldn't make you to stake more than your budget, it isn't the amount you stake that determine if you're winning or not, it's the knowledge of the market that you have and how you make use of it.