My brain is fuzzy and have zero motivation now. How do I turn this day around and become productive?
By taking a break and changing your state. Sounds counterintuitive.
But, take a real break, getting off all electronics.
Go for a walk, run whatever, just get active and change your state.
Listen to that song that brings you back to that place and time when it was perfect and exciting, get your head in a space of positivity and motivation, however you do that.
Then get to it with laser focus.