Happiness is a full tank is about cultivating happiness in one’s own life. This includes understanding the positive emotions that lead to a full tank, such as contentment and joy.
Some skeptics argue that a concern with happiness is simply hedonism, but they might be mistaken if they assume that only pleasure matters for human well-being. Happiness is a full tank might also involve virtues such as wisdom and knowledge, courage, love, and finding meaning in unavoidable suffering.