Thanks to animator/writer/director and all-round nice bloke Pat Sarell for this insight.
Junior artists are fueled by passion for what they do, through they may not have the skills, technique and knowledge to do it well. So they train to become better.
Mid-level artists learn the skills to become more competent, but in doing so they also learn to follow rules, particularly those that play to their strength and help them avoid aspects of the work that they are less adept at. Their knowledge of how they should work and of their competencies constrains them, and often with those constraints the passion that once drew them to their art fades.
Senior artists have developed sufficient knowledge, confidence and have broken enough rules over their career to have freed themselves from the constraints that held them back as mid-level artists. They can now re-connect with the passion they first had, but with the ability to fully execute on their ideas.
If you’re at a place where you’ve lost the passion for what you do, don’t give up, you will find that passion again. Now’s the time to dig deep, keep learning, know that you’re on the path to becoming a senior artist and that the path may not always be a straight one.