If the 2-way interaction between the left and right hemispheres of our brain is hindered or blocked, we have to invent other, often inappropriate, neurological pathways. This often inhibits our ability to think clearly or to perform everyday tasks such as making choices, relating to others, and making sense of our world. These determine to a large extent who we are and how we live our lives.
If our brains are not integrated, we may experience life as a struggle. The more detours messages have to take to get to their destination (because of blockages, compensations, and adaptations), the slower and more stressful brain processing will be and the more energy will be wasted. Look at it as the difference between travelling on a straight, wide, tarred motorway, or taking the twisting, turning, narrow, bumpy dirt roads through the country.
Some reasons for a loss of brain integration include acute stress (related to a specific event, person, or situation), experiencing trauma (as well as remembering or re-living past trauma), and shutdown of the corpus callosum which frequently starts as a defense mechanism during childhood but subsequently leads to difficulties handling life.