What is meant by the line 'Tread softly because you tread on my dreams' by W.B Yeats?

"I have spread my dreams under your feet,

Tread softly because you tread on my dreams."

It's a declaration of love for his muse and life-long love, Maud Gonne (the one person who had to be gentle with him lest she should trample and destroy his dreams and ideals).