Even music legends get writer's block, sometimes!
Sting recently spoke to The Guardian about his songwriting process. Apparently writing music comes fairly naturally to him, but the lyrics are what he has the most trouble with. To cope with this difficulty, he uses "free association," in which you write down anything that comes to mind. Essentially he throws all his ideas to the wall and sees which ones stick.
Sting's biggest piece of advice? "You have to be brave, in a sense... And just start." So get to it, lyricists!