Lonely Hearts. It gives the idea of people who are alone and perhaps feeling sad because of their lack of connection with others.
Fading Hopes. When hopes start to fade, it's a sign of disappointment and often sadness. This title can be great for a sad story where the main character is losing hope in life or a particular situation. For example, it could be about a person who has been trying to achieve a dream for a long time but keeps facing setbacks and is slowly losing their hope of ever achieving it. The story could detail their internal struggle and the downward spiral of their emotions as their hope dwindles away, which would be a very sad tale.