If you ignore history, you'll likely have to learn its lessons the hard way.

learn the hard way 是一个英语固定短语，字面意思是"以艰难的方式学习"，实际含义是"通过亲身经历困难或失败来获得经验教训"，强调不靠别人告诫，必须自己吃亏才能真正学会。