I like this list, even though I have to comment on a few points in specific.
5. Adding to thiw, I've made the experience that I play better when eating while playing. For example, I'll prepare a slice of bread before playing seriously. Then, right before starting the map, I'll take a bite. Whenever I finish a bite, I'll take a new one as soon as the map allows me a break. Don't ask me why that's supposed to help, I just randomly stumbled upon it in multiplayer when I was hungry and discovered that it worked for me, so it might work for others as well, right?
6. I partially disagree on this one. Playing a map over and over again gets you into a certain flow, which enables you to play that map better while in that flow. However, it's also important to realize when you cross the point where you get tired from repeating the same thing over and over again. It's some kind of "know your limit".
7. A great tool for that is to enable the UI. Not only does this hide your combo, it also hides your HP, both of which used to bother me if they got high (combo) or low (HP). After a while, I was able to reactivate the UI without getting stressed out from that information. Another thing that I found to help is to colour the UI elements red, since red is a low-energy colour, so it's getting less of an obvious thing for you as well as being less stressful for your eyes to look at.
8. Don't try to play as good as possible. Try to improve as good as possible. Not only does this help against falling into point 2, it also allows you to feel great when you improved at a certain map while still not achieving 'good' results at it.
9. This goes somewhat hand in hand with point 8, but put youself some goals. When I started, I had three different goals. First, super-longterm goals. For me, that's currently Freedom Dive and Big Black, even though I'm still faaar from that level. They are mainly motivational, since they're supposed to be way out of your league. Second, mid-longterm goals. The very first map that my friends let me play was Pretender. Of course, I failed miserably, with even the intro being far too fast for me. However, I occasionally played this map, and it was a great feeling to slowly being able to pass more of it. Now, I recently was able to clear it, and my next mid-longterm goal is Scarlet Rose. These goals are also great for motivation, but they actually provide direct training possibilities. Playing Pretender so many times while I clearly wasn't able to clear it definitely increased my reading abilities, especially how fast I was able to read. Third, there are the short-midterm goals. For me, this started out with Kokou no Sousei [Hard], and currently it's 21st Century Girl. These are the kind of maps that are only slightly above your level, the maps that you can repeat over and over again. For these goals, it's important that you want to reach a full combo in any case, and the best accuracy you can. Heck, I didn't leave Kokou no Sousei until I managed to SS it, which again greatly improved my accuracy abilities.
10. Don't be afraid of maps. I see this very often especially with old maps. Now, of course I have to agree that mapping quality has increased and all that. However, avoiding an entire class of maps simply because they aren't mapped greatly makes you loose out on all the experience those maps deliver. The thing is that such maps need a different skillset that modern maps, so not playing those maps makes you skip out on these skills. You don't have to love such maps and you don't have to play them often, but don't completely disregard them and play them once in a while.
11. Now this isn't mandatory, but doing some kind of sports is a great help too. Not only does it grant you more mental stability, which helps against point 2, it also helps you get into a competitive mindset and grants you stamina. What kind of sport isn't very important. Heck, even seriously playing piano or singing would qualify for this (believe me, they ARE pretty though when done seriously. If you disagree, I bet you never practised playing piano for two hours straight or practised singing for one hour - it goes on your substance just like 'proper' sport). Personally, my main aspects of sport are playing piano and jogging, but again, the specific kind of sport isn't the important thing.
12. I get that this is not the point of your list, but it's also important that similar mental factors directly affecting the gameplay that are worth to look into.
