Studying maths in my undergrad and doing some community building in Germany and Berlin as a volunteer.
I don't think it's just a "nice excuse", I think it makes sense to celebrate if you got rejected by an EA org. The work you wanted to do to help the world is being done better than you could have done it (assuming their application system works well enough). And you don't even have to lift a finger. That is not to say that I would predict myself to react in a very positive way immeadiately after rejection, but it's how I'd want myself to react.
This article really helped me getting these things clear in my head! Thank you :)