Listen to your body. If you are feeling sad, check in with someone else. If you notice your overall vibe heading towards the black hole, take all necessary evasive actions.
Whatever you know about depression, make sure you only talk about your own experience and don't try to prescribe or preach to others about their tranquilizing meds.
I'm not perfect. I don't have the answer to this question of how to be happy all the time. But I am learning to see my emotions, my feelings, as something that are a part of me, but are not all of me. That's my meta-view.
If we can rise above our present distress and the distractions of our disappointments, we can appreciate all the layers of the present moment. It's all cake. It may not all be delicious. But our attitude about the cake colors every one of our present moments. It's our attitude about the cake we're being served that gives us the freedom from suffering.
Max Powers, today, is walking into the 2019 Holiday season with a much better plan. Take care of all the things you can take care of. Work your program. Let go of the things you cannot control.