世事难料： 最简单： You never know what is going to happen (in life) 别的成语和习惯用语： "expectedly unexpected": It means The only thing certain in life is uncertainty. It emphasises that life is unpredictable. "You never know, lighting could strike" / "You never know when lightning is going to strike"： It is an expression which means things can be as unpredictable as lightning. That it can happen at any time. "Never know which way the wind will blow": Some people say this to describe unpredictability of things. However the more common saying is "know which way the wind will blow", which means try to anticipate what will happen so that you are prepared.

难料 是啥？

things change,roll with them. ps:roll with them means"随遇而安”

世事难料=You never know. /The unexpected always happens. Don't be so pessimistic. You never know where you might end up.别那么悲观。世事难料，你永远也不会知道最后你会去哪里。