Milan Kundera famously wrote about the "Unbearable Lightness of Being." And his novel does an admirable job of showing just how light and ephemeral our lives can be.
There's also the "unbearable heaviness of being" too. There is a real gravity that keeps our feet on the ground, and there's a heaviness to certain events in our lives that ground us, or put us under the ground.
So yes, we must bear the lightness and heaviness of being; both of these "states" dance around us like light and dark moths to our little flames. And even if it's all "unbearable," we really can bear both the lightness and heaviness. We can, and we do.