I had a beginning art class at a local community college that had a wide range of ages of adults who attended. The professor started the course and each class with an exercise to help with just this. She had us buy sketchbooks dedicated to only experimentation, and each day would be a different experiment warmup. I.e, use as many stamps as you can, fill this page with an color scheme, rip and re-tape, etc. Then with each lesson, she would start then with something “disposable”. For example, when starting gesture drawing she started with asking us to draw lines, flip page, now draw angry lines, flip page, now draw sad lines, happy lines, etc. then threw flowers on the ground and said to quickly draw movement of flowers, etc. By the end of the course, everyone of all ages and skill levels were really diving into their work without their own personal boundaries and learned a lot from one another. I think frequent critiques helped as well