Great post about a subject that is near and dear to my heart. As someone who has been a successful songwriter and music producer I agree with all of your points wholeheartedly. I would like to add two more that I think fit into what you are saying.

1. Build a support system. You need people around you who encourage you when it gets tough, you get bored and when you hit those plateaus. Without this many simply get turned off. I am going to begin my 9 year old on piano this year and I know that unless I become a support system and find others to as well, she will not stick with it even though I know the benefits for her if she does so getting a support system is critical in my opinion.

2. Take a break. We all need to get away from something no matter how much we love it because when we do we come back with a fresh perspective that we can bring to our creativity. If I was in the studio with a great singer and we could not get the lead vocal I would sometimes take the day off and do the most random things. Sometimes I would take them to a movie and once a theme park. The idea was to get it out of their head for a day. It would always work. Not only was the pressure relieved, they would have different ideas about how to approach the music.

Sorry not trying to take away from your wonderful post, just want to add some things that have worked for me. Thanks again.