What track has pulled the biggest 180 to you personally over time?

Example: I grew up listening to American Idiot as a young teenager, and I always chalked up Whatsername to being the weakest and most skippable song on the CD, hence why they stuck it as the last track.

Now over a decade and a failed longtime relationship later, Whatsername is one of my absolute favorite, bittersweet, & emotional songs of all time, regardless of band.