Quixotic:

1: foolishly impractical especially in the pursuit of ideals; marked by rash lofty romantic ideas or extravagantly chivalrous action
2: capricious, unpredictable
Etymology:
From English: Quixote, a visionary, after Don Quixote, hero of a romance by Miguel de Cervantes

I love that such a colorful adjective was spawned by a fictional character!

Everyone should “tilt at windmills” and engage in some sort of Quixotic behavior at some point in their life.