Complex sentence: My psychologist explained in the simplest of terms is that you can alternate your breathing in ways that can lower your heart rate and how holding your breath a certain way can help you release chemicals that slow down release of adrenaline and cortisol.
Split into simpler sentences: My psychologist explained in the simplest of terms is that you can alternate your breathing in ways that can lower your heart rate. Additionally, I learned how holding your breath a certain way can help you release chemicals that slow down release of adrenaline and cortisol.