Why do all good things come to an end???

"Well, the dogs were barking at the new moon
Whistling a new tune
Hoping it would come soon
And the sun was wondering if it should
Stay away for a day
'Til the feeling went away
And the sky was falling
And the clouds were dropping
And the rain forgot how to bring salvation
The dogs were barking at the new moon
Whistling a new tune
Hoping it would come soon
So that they could die"