Thank you for the opportunity to help you with your question!
work life balance ensures that during training a trainee is able to optimumly train and correspond to work and work environment without external deterrence such as home affairs that impact negatively.
work life balance dictates recruiting and selection through acceptance of an employee to comply to stipulated procedures that may work negatively on his side, this is a key influence in retaining an employee too.
work life balance is a key to performance as productivity at work has psychological contribution and general perception of output required from a worker.
Please let me know if you need any clarification. I'm always happy to answer your questions.