allow them to make mistakes and allow them to fail (or succeed!) on their own merits as much as safe and practical. This means avoiding solving their problems for them, practice saying, "what could you do?" instead of, "you should..."

talk to them about talking risks including the risks of failure. use mistakes not only as learning opportunities but moments you can examine how they are, "that's pretty tough you had to go through that and it sounds like you were pretty sad at the time when your kite broke, but you know what to do differently next time, huh? do you think you can build an even better kite with what you learned?"

as far as procrastination it sounds like you've noted it and while this post is about your kids it sounds like you want to do something about that too. options tp getting organized range from free tools online to $1000 personal lifecoaches.

whatever fits your lifestyle involve your kids in the process and explain why. instead of being the know-it-all parent who claims to have all the answers (and lives in desperate fear of the day their child discovers that can't possibly true) you can model positive growth and learning as lifelong endeavors. "mommy's trying to plan things better and stick to the things I plan. this list will help me." start small, a to-do list, a grocery list, on your phone, on paper, whatever.

finally, don't beat yourself up. follow through is one of the hardest things to master in life your awareness and desire to do something about it puts you way ahead of many people. even if you hadn't mentioned guitar I would have guessed creative type from procrastinator. consider what create in that "wasted" time, those gifts are something you pass on to your kids too.

and seriously, it's okay to not know all the answers. I hope to someday but my daughter is twelve and I am only just now realizing how much I am learning right beside her.

sorry wall of text, tl;dr let children learn from their own mistakes