a person who is regularly exposed to a certain environment or risk will inevitably be affected by it

他在灰色地带游走多年，最终还是被捕了，真是常在河边走，哪有不湿鞋。

the tendency for those in positions of power or temptation to eventually succumb to corruption or moral compromise

作为采购主管，他终究没能抵挡住诱惑，正所谓常在河边走，哪有不湿鞋。