Work or play?

"You have achieved success in your field when you don't know what you are doing is work or play."--Warren Beatty

My professor wrote this quote to me when I told him that I was struggling with writing. How to write a paper well is something I have problem with all the time. I do not think I can enjoy the work as much at this stage. I was literally intimidated by the job--writing a paper. My problem is to write a good one, not a mediocre one. I guess sometimes I just have to let it go, living with imperfection, and admiting that it takes time and practice to be better, better, and better.