Twitter makes you anxious because it’s a steady stream of open loops and potentially actionable material that overflows your mental inbox. Your psyche thinks it’s getting assigned a todo list it can never complete, (esp if you follow good accounts) while drowning in “unreads”.
— Daniel Kazandjian3
I find that in digital environments, the ability to hold strong mental boundaries, i.e. boundaries in one's mind, becomes incredibly important to manage your time and energy. For instance:
Prioritization: boundaries about what matters and what doesn't. Not everything is equally important, and those who cannot prioritize are destined to burn out or never get started with the things that really matter to them.
Mental closure: boundaries about what you're done with and what is a work in progress. This is downstream of prioritization of course, because there is no point completing a project you don't care about, especially if you didn't even personally decide to care about it in the first place. (see the tweet mentioned above)
Compartmentalization: boundaries between different settings, such as work versus private life, or work and personal projects, or sleeping and waking time. There is a time for work, and there is a time for rest. The worst thing possible is to constantly be in that awkward middle where you aren't resting, nor are you being productive.
All the sub-skills blend into one another, such that getting better at prioritizing means you'll discard projects or notes that don't really matter, such that it is easier to complete your projects, both in the real world and in your mind, and easier to shut down at night when you need to sleep.
I find that minimizing is really the best way to start with a better mental hygiene, though you might find some resistance. In my case, I had a severe case of bookmark and note hoarding, which I understood the root cause after several years: a part of me was trying to control my life by acquiring a lot of knowledge. Of course, this doesn't work, but my controlling mind believed it more and more. “Just one more video, just one more book, and surely I won't have to feel scared anymore!”
As a result, I decided to cut out a bunch of stuff if it wasn't obvious that it was useful in my life, and if I did find the general direction of an idea to be useful, I would keep a few pointers in folders or notes that are for later. What you find is that most things aren't super important to keep. The things you really learn are from personal experience anyway, and there is no way of living that prevents failures and suffering. Better to focus on avoiding the biggest traps in life, those that create really awful situations that require many years to get yourself out of. Most problems or traps are not like that, so stressing too much about avoiding every single of them will very likely only lead in paralysis and fear.
To conclude and see the importance of all of this, here are some failure modes and consequences of poor mental boundaries:
Bookmarks and notes hoarding
Mental tiredness
Inability to see what is actually important versus what isn't
Background low-level anxiety because you feel like you "should" be doing something but you aren't, which also blends into a background low-level tiredness
Footnotes
2 Which is something that many people are terrified of doing, or I guess non-doing.