Whatever activity is undertaken (by beings) is the movement of desires. (Manu Smriti)
The self is identified with desire alone. What it desires, it resolves; what it resolves, it works out; and what it works out, it attains. (Brihadaranyaka Upanishad)
At first in darkness hidden darkness lay,
Undistinguished as one mass of water,
Then That which lay in void thus covered
A glory did put forth by Tapah!
First desire rose, the primal seed of mind,
(The sages have seen all this in their hearts
Sifting existence from non-existence.
Its rays above, below and sideways spread. (Rig Veda Nasadiya Sukta)