Some days…many days…you feel creatively and motivationally drained.
It feels as though you have nothing to give. Nothing to provide. You can’t conjure up any words or ideas which are useful.
The only solution: just start writing (or whatever it is you’re trying to do).
It may only be four crappy lines; but after those four lines, you’ll realize that before when you said “I can’t write anything,” it was complete horse shit.