I would just add one comment about the "finding a critical, supportive friend" advice.

No matter how close you are to somebody, it can be very difficult to offer honest criticism - because you can't gauge the reaction, and the reaction may well surprise you. I offer an example:

There's a performer in my area who goes around the various sessions and clubs from time to time. He cannot sing. He can't hold a tune in a bucket. All the melodies he sings - or rather tunelessly chants in a monotone - sound the same. Some friends of his once raised the topic with him, in a supportive and gentle way, and he very quickly became irate to the point of near violence. They were completely surprised - and regretted having offered an opinion.

Someone may ask for an opinion on their playing - but don't be surprised if they get huffy about your honesty!

As Rick Wakeman joked in one of the TV "Grumpy Old Men" programmes:

"My wife came downstairs with a red dress and a blue dress and asked me which one I preferred. When I said 'The blue dress', she snapped, 'What's wrong with the blue one?'"