Why trading seems to be difficult ??

Fianancial market management is the only business ,where investor or a trader can take decision of max loss he /she could bears , while in offline business seems to predict how much max loss we could experience ! because we can build a house then after we could even face will a earth quake and losing 100% of that house, in my experience of above 5 years , what i have see in this industry, most people spend their decades and decades trying to master a winning system and ignoring that , fixing their mental state or their psychology is the most password! the second security no one is engaging in learning how to choose market to trade.