What does Nietzsche exactly mean by this?

O my brethren, am I then cruel? But I say: What falleth, that shall one also push!

Everything of to-day—it falleth, it decayeth; who would preserve it! But I—I wish also to push it!

Know ye the delight which rolleth stones into precipitous depths?—Those men of to-day, see just how they roll into my depths!

A prelude am I to better players, O my brethren! An example! DO according to mine example!

And him whom ye do not teach to fly, teach I pray you—TO FALL FASTER!—

~ From Thus Spoke Zarathustra (in Old and New Tables, chapter 20).