27. Spend a few minutes each week or each month working on some instructional material. Doesn't have to be for harmonica. Just work on something unfamiliar.You're going to eventually develop your own practice routine. Perhaps early on you'll be searching around for something that suits you. Maybe you start working on Jerry Pourtnoy's material, or perhaps David Barrett, Richard Sleigh, Adam Gussow, or Ronnie Shellist turn out to be 'your guy'. (If any of these names are unfamiliar to you, search for them on YouTube).
Whatever you work on consistently, it's important to vary your routine. Reach out for something new and unfamiliar. You don't have to torture yourself with it or get sidetracked from your routine (because routines can be important to learning), but it will help you to keep your perspective to focus on the unfamiliar on occasion. It's refreshing, invigorating.