What is the reason for the activities described in lines 1 to 4 of the poem?

The vivid grass with visible delight Springing triumphant from the pregnant earth, The butterflies and flowers in brief flight Dancing and chirping from the season’s birth, 5 The dandelions and rare daffodils That touch the deep-stirred heart with hands of gold, The thrushes sending forth their joyous thrills,- Not these, not these did I at first behold! But seated on the benches daubed with green, 10 The castaways of life, a few asleep, Some withered women desolate and mean And over all, life’s shadows dark and deep. Moaning turned away, for misery I have the strength to bear but not to see.