There is no such thing.
The environment will never be quite right.
Your emotional state is never going to be perfect.
If you wait for inspiration, it is likely never going to come.
Instead, push through.
Show up, sit down, and type (SUSDAT).
The magic happens most of the time after you show up. You write something bad and then your mind keeps working after you finish. You go about your day and suddenly realize what your little piece of bad writing really needs: a word, a phrase, a sentence, etc.
Then you return to that uninspired piece of work and realize it wasn’t as bad as you thought. It needs some work, of course, but its salvageable.
Compare this to nothing at all.
If you wait for inspiration or wait for the mood to be just right for creativity, the page will remain empty.
Inspiration comes to those who work not those who wait.