Every time you start a drawing, trust the image will come. If it comes unwillingly, coax it out. Gently but firmly. If it still doesn’t want to reveal itself fully in front of you, be patient and understanding. Frustration only leads to despair and failure.
When the image has come but you know it can still be perfected. Be firm and strict and demanding in order to whip it into shape. But only do this if it has been allowed ample time and space to play and indulge in its conceits.