what do institutional traders know that retail don't?

Trading was not originally designed for retail players because for most it is just a zero sum game. Institutional traders have access to specially designed economic models that can analyze an asset thoroughly and predict with some level of accuracy, which way the market is headed for the period under review. Retail traders don't have access to such high-level tech and are basically bringing a knife to a gun fight.

Institutional traders have been able to solve the problem of psychology by creating and enforcing daily loss limits. Once an institutional trader makes up to 3% loss in a day, the trading platform automatically shuts him out. retail trading software does not have this feature, so retail traders are allowed to self-destruct aka blow their accounts

True, institutions enforce daily loss limits to protect capital from emotional spirals.