The importance of maintaining a work/life balance is not a myth. If you give too much of yourself to work, you get burned out — sometimes both at work and in your personal life. Health and relationship issues arise from these conditions.
When we tip the balance too much toward work, it is usually because we are seeking perfectionism. The more you are involved in family and work, as they both grow, the more elusive perfection becomes. Think about this: Are you rewarded by perfectionism or by productivity? Start leaning toward productivity.