What's the best writing advice you've received?

Keep ideas flow freely.  Worry about organizing, editing and proof reading after.

Write something every day. 

‘Don’t get caught writing that obscenity on important monuments’

...was the best advice I’d received

That 90% of what you write, even though you believe it is a great work of art, will be rejected. And many times you just do not know why. 

Don't give up your day job.

"Write what you know."  

Write it out in 'rough' first,  then you can check your spelling and grammar.

Most of my poems are about the Vietnam War .. 

I've had veterans praise my work and encourage me to keep writing because I help to bring

their experiences to life for those like me, too young to know that period in time ourselves.

Excellent writers are excellent readers.

Reading not only expands your vocabulary - a strong vocabulary is essential to writing - it exposes you to many more ideas, many different ways of thinking.

I don't really think writing advice can stand alone, but for me, personally, it would be: Write every day.