I have decided that there is a difference between "choosing to be happy" and being of good cheer. One cannot nor should not always choose to be happy. If so, we would never mourn with those who mourn, we would never experience the sobering, tutoring process of loss, and we would not experience empathy for those who struggle or who suffer pain or injustice or abuse.
On the other hand, to me being of good cheer as found in the 16th chapter of the book of John means possessing a grounded, calm sense of peace, laced with hope, that is pretty constant in both times of celebration as well as times of deep sorrow, fear, confusion, anger or suffering. It enables us to act positively and calmly and effectively to navigate those struggles in our own lives and to assist others with more open eyes and hearts.
Good cheer dwells comfortably with and deals peaceably and carefully with the reality of a far from perfect existence and the loss of dreams. Choosing to be happy too often tries to pretend that those imperfections and losses should be ignored or glossed over, which, I believe, can actually prevent our spiritual growth.
So, with the grace of God, I will not "choose to be happy" but I do hope to be "of good cheer".