The speaker feels happy, but also knows that her happiness is temporary, dependent on good circumstances and a good mood. The change is inevitable, with the loss of mood and the imposition of difficulties. Hence, “this happiness / Is provisional.” In a mood of happiness and satisfaction, the difficulties mentioned in lines 3 and 4 seem distant and unimportant (at least temporarily), even though they are still within the speaker’s consciousness. We may assume that the verbal noun “Being” in the title takes into account both good and bad circumstances. Life is neither all good nor all bad; it is a mixture of both.