Can you ever be "good enough" in any area of life? Can you ever be content to settle and enjoy your progress--in either your personal or private life? Sadly, the answer is probably "no".
Personal development and growth is a MUST for better relationships. Professional development is vital for those who want to excel at their jobs. For writers, no matter how good you think you are, you can always be better!
It's never enough to just be "good" at what you do--in this case, writing. You may feel like you've made a lot of progress over your career as a writer, and you're content with the way your writing has improved. But the moment you think you're "good enough", that's the moment the quality of your writing begins to decline.
It's just the way of nature! If you're not making forward progress, you're sliding backward--back into old, bad habits. You can't accept that your writing skills are ever "good enough", but you have to constantly be searching for ways to improve. The more you work to improve and learn, the better you will become.
How can you do that?
Read more. The more you read, the more you see what other authors do--both the good and the bad. You'll learn what to do, but you can also learn what NOT to do!
Put your work in front of others. It's always wonderful to have people to tell you your work is wonderful, but you don't need more "yes men" in your life. Find people who will tell you what's wrong with your work, and who will call you out on poor quality. Those are the kind of people you need in your life in order to make progress!
Create more. The more you create, the more you push yourself to do more and be better. Writing more is the key to getting better at writing, so you should always be working on something.
Study. Study the craft of writing. Study grammar, syntax, and punctuation. Study flow and pacing. Study marketing and promoting. Study self-critiquing and editing. Study querying agents and publishers. Always be learning something new about the industry, and you'll make forward progress in your career as a writer.
It's never enough to be "good". If writing has taught me one thing, it's that you always need to be working to improve and grow!