So, I've been playing in this game for a couple of sessions and having plenty of fun. But when I approached the DM about how to proceed with my backstory (simple enough revenge plot), they told me that they weren't planning on incorporating backstories into the game. Now, I wouldn't mind if I knew this before, but we spent quite some time before the game talking back and forth to make it fit the setting and would have made something different or not made the effort if I knew it would not matter.
It has kind of drained my interest in the game since I feel weird playing a character with a dead motivation now.
Any advice on how to regain my lost interest?
Edit: I feel I need to be clear: I don't mind playing a pc with a backstory that doesn't relate to the game. Problem is that it went from building a backstory with the DM explicitly saying "Pc is hunting X for revenge" to "don't bother asking about X, not gonna include that in the game."