I come and I go, more than once in a day.
Yet I've always been here; for eons my stay.
A bearer of life, I bring fear and great dread;
A destroyer of old, millions by me are fed.
Artists and poets my presence inspires,
My moods, they are varied, my journey ne'er tires.
Once I was greater, but my time comes again.
Can you yet name me, my riddling friend?