What's the most disappointment you've ever felt?

My friend texted me today, asking me what I'd do if I found out one of my friends liked me and wanted a relationship. I thought she was being serious and knew of someone who had feelings for me. I was elated and desperately wanted to know who this anonymous person was. It turned out she was just curious and asking random questions. Now I feel undesirable and lonely.

What did you get excited for, only to find out things weren't what they seemed?