Is it possible to have joy and sadness in your heart at the same time? I think so. Is it possible to have happiness and sadness in your heart at the same time? I don’t think so.
It seems to me that joy is a state of being. I have an eternal joy in my heart that is a direct gift from God (a “fruit” of the Holy Spirit), a result of being His child, by my own personal decision/choice. Because that joy is given for eternity, the joy never leaves. My state of being (who I AM) is always full of joy.
But happiness is something entirely different. It is a state of mind, a temporary state that can be caused—and controlled—by individuals and circumstances. The same is true for sadness. I can determine my own state of mind, to a large extent. I can allow circumstances to manipulate my state of mind-- but not my state of being.
Are Christ-followers sometimes sad? But of course. The sadness can even overshadow the joy at times, if sadness is allowed to become more than a temporary state of mind. Even David prayed that God would restore to him the joy of his salvation (Ps 51:12). But the joy is there, in the heart, ready to be restored, at any time the individual is ready to rely on the state of being rather than the state of mind.
So, my answer to my own question is this: While it is not possible to be happy and sad at the exact same moment, it IS possible for joy and sadness to coexist in the same heart at the same time.
Sometimes I am happy. Sometimes I am sad. Always I am joyful.
But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith…Galatians 5:22.