If you keep on dwelling on negative thoughts then it will just bring you down further, take this as a lesson and learn from it in the future. Ultimately it will be your choice between Rugby and Boxing, your family should be happy and accept whatever option you choose. Just keep at it and train so when the next opportunity comes, you will be ready.
Jessica, are you a guy or a girl ? I'm guessing boxing and rugby doesn't match your name and profile.Anyway, is missing a tryout in rugby really worth hating yourself over ? Sit down with your family and discuss this issue is my best advice to you.