The secret that real writers know that wannabe writers don’t: It’s not the writing part that’s hard. What’s hard is sitting down to write.
Book: The War of Art
Sitting down to write is way more difficult than writing. Of course, writing is hard, and writing well takes a lot of effort. However, it's much harder just to sit down and write against procrastination without any single burst of motivation. When we already sit down and start to write, writing is not that hard anymore.
Haruki also mentioned in his book, What I Talk About When I Talk About Running: A Memoir, that the great mystery writer Raymond Chandler once confessed to him that even if he didn't write anything, he made sure he sat down at his desk every single day and concentrated.