Here's a metaphor:

The first day of writing anything is a lot like the first night of a marriage.

So much expectation.

So many ways to begin.

So much unnecessary pressure.

The truth is no novel or tagline or treatment or strategy unfurls itself perfectly the first time you start writing. No creative effort has read your mind and quieted all criticism before its first reveal.

Imperfection is part of the charm of getting to know your idea (even if you've been dating or living together for a while).