Taking lessons or coachings from a teacher is a big part of our growth as musicians. The amount of information on technical and musical elements, and their experiences, that are available to us is priceless. However, this is not the only way for us to learn. Masterclasses, books, videos, podcasts, etc., are very helpful and give you more perspectives on certain aspects of your playing; it's good to have that variety in your tool box. Still, one source of information that we don't always take advantage of is our peers and colleagues. Often, they are either doing equally as well or are further along, and they may have found or experienced things that may help you reach certain goals. The fact that you both are working to achieve similar goals is motivating, encourages mutual support and offers opportunities for constructive criticism.
As I work on an audition list, I send recordings on the first day, to a close friend with really good ears, to have them critique them. Yes, it's only the first day of preparing, but it's good to both have someone keeping tabs on you and also to see where you are physically, mentally and musically. Each time that you do this you'll both see and hear the progress, no matter how small. So I encourage playing for your friends and also returning those favors to them as well. Having a buddy on this journey of bettering our musicianship can make it a lot easier than just going alone, and the more friends you have, the more fun it can be.