To be "happy for a moment but sad for a lifetime" describes a situation where someone experiences a brief period of joy or happiness, but it is overshadowed or outweighed by long-lasting sadness or sorrow throughout their life.
This expression can be used to illustrate the contrast between a fleeting positive experience and the enduring negative emotions that follow. It suggests that the moments of happiness, no matter how significant or joyful they might be, cannot compensate for the overall sadness or unhappiness experienced over an extended period.
For example, imagine someone who experiences a brief, intense love or achieves a significant personal goal but later faces a series of tragic events, heartbreak, or loss that leads to perpetual sadness. The happy moment becomes a mere memory, and the sadness becomes the dominant emotional state in their life.
This phrase highlights the idea that happiness is not solely determined by isolated events or moments of joy; rather, it is the overall contentment and well-being that matter in the long run. It also emphasizes the importance of addressing and coping with the underlying sources of sadness and finding ways to cultivate lasting happiness and fulfillment.