You left a letter as a clue.

Day 05 - A thank you letter to someone who has changed my life

Thanks to you, I'm stronger, smarter and happier.
But...
Thanks to you, I'm weak, stupid and sad.
Because thanks to you I have fallen for you yet I can't have you.

Am I holding onto something that will never happen
Tell me have I fallen deeper than I should
I don't want to say goodbye
But can't hold onto chances now
I gotta hear yes or no
Oh, am I falling in love alone