I have a 6 month old Boxer, Cassey. She's great, but refuses to come back when I let her off her leed.
This maybe my fault as in the past, when she's been enjoying herself, running around the park I've called her, she came and the first thing I did was put her leed on ending her fun.
She has jumped in a lake and ran home when spooked by another dog when she's been off her leed. Now I scared to let her off at all incase she hurts herself.

Please help!

Michael.

The best thing you can do is go back to basics take her to a enclosed area where she can not injure herself if she doesnt come back and practice recalling her giving her a treat and then letting her go off to play again so she doesnt associate you with the end of her fun!
It may take some time but be patient and you will get there in the end.
You may also find puppy training classes very helpfull
good luck and stick with it