I've posted this before, but I can't think of a sadder song for me, so it's still my answer. Sorry for those who might have already seen this.

This won't make sense without some backstory, but you asked for sad so I promise to deliver.

Birthdays meant a lot to me, and my sister growing up.  They were your holiday and yours alone, when gifts were given and the menu and agenda and were all yours to set.  No matter what else arose, birthdays cheered me up.

But times moved on, and I moved too.  I found myself in a new town, Boston, with my then girlfriend Jane.  I can no longer recall why times were trying before my birthday, only that they were.  But I knew my birthday would cheer me up.  It came and nearly went, all without mention. My parents hadn't forgotten, we had plans later that month.  Life gets busier as you get older, and that's when we could make it work.  But no call came nor an email either to remind me happy birthday.  I had moved with Jane, and recently, so had no other friends. Even she forgot the date.  Though again we had later plans, again disappointment.  After looking forward to birthdays all my childhood it was a letdown right when I needed something to pick me up.  I went to bed early and depressed.

At 11:30 I awoke to my ringing phone, but did not make it to catch the call.  My sister left a voicemail singing happy birthday.  She could never forget something so special. Knowing that, and hearing her call made the day all worthwhile.  It was her hallmark to be so thoughtful and so caring, even though she was half the world away in med school in New Zealand.  Late as the hour was, she alone was not late.  She was the only one to not forget the date. 

She had almost finished her residency a few years later when she stole the syringe she used to kill herself.  Her death was intentional.  She left 32 notes, one for every person for whom she cared and one for each who cared for her.  It was so like her to always care, even in her final act.  At her funeral, I had that thought.  She was no longer there to care, no longer there to remember when everyone else forgot.  It was up to me now to never forget her.  Sitting there in the hardwood pews I heard her sing that birthday voicemail in my mind, but no longer happy, now slow and sad, a minor tone to the tune.  And I wept. 

The song wrecks me, even now.  There in the middle of the birthday party, alone in the celebration, a tear slips down my cheek as I hear her sing and remember my sister, the one who would never forget.