The phrase "the triumph of hope over experience" is a common expression that means people are often too optimistic about future events, despite evidence to the contrary. Full definition
It's «the triumph of hope over experience, just like a second marriage.» (businessinsider.com)
Oscar Wilde famously remarked that a second marriage is «the triumph of hope over experience,» but both partners in this case seem mature enough to cope. (foreignpolicy.com)
In the words of the 19th century Irish poet Oscar Wilde, it is «the triumph of hope over experience.» (punchng.com)