Boredom Is a Skill You Used to Have
It was never pleasant, and it was never supposed to be. But the capacity to sit in an unstimulated minute turns out to be load-bearing for almost everything else.

Try this, and be honest about the result: stand in a queue for four minutes without reaching for your phone. Not as a discipline exercise. Just stand there.
Most people cannot do it. Not will not — cannot, in the sense that the hand moves before the decision does. The interesting part is not the failure. It is the discovery that something you did effortlessly for the first two decades of your life has quietly become difficult.
Boredom was never enjoyable. That is not the claim. Anyone romanticising the long Sunday afternoons of childhood has forgotten how genuinely unpleasant they were. The claim is narrower and stranger: the ability to tolerate an unstimulated minute is a capacity, it can be lost through disuse, and a surprising amount depends on it.
We did not decide boredom was bad. We just found something cheaper than sitting in it, and took the deal every single time, for about fifteen years.
What it holds up
Start with the obvious one. Any work of consequence has a middle section that is tedious. Not hard — tedious. The research is done, the idea is clear, and now there are four hours of unglamorous assembly between you and the finished thing. People who can sit in tedium finish things. People who cannot start over, repeatedly, always at the interesting part, and accumulate a great many beginnings.
Then the quieter one. A mind with nothing to process starts processing. This is not mysticism; it is what idle minds do. The thought you have been avoiding surfaces during a walk, in a shower, on a train with a dead battery. It surfaces there because those are the only places you have left it any room. Fill every gap and you do not stop having those thoughts — you just stop having them where you can hear them. Some of the things they were going to tell you were important.
And the one nobody mentions: boredom is how you find out what you actually want. Desire needs a vacuum. Given a genuinely empty afternoon, you eventually do something, and the something is informative. Given an afternoon with a feed in it, you do the feed, and learn nothing about yourself at all.
Getting it back
The rebuild is not a digital detox, which is mostly a way of dramatising the problem rather than fixing it. It is smaller and considerably duller.
Pick the gaps you already have and stop filling them. The queue. The lift. The three minutes while the kettle boils. Waiting for someone who is late. These are not opportunities to catch up on anything; they are the last unstructured moments in a normal day, and reclaiming them costs nothing.
Expect it to be unpleasant, and expect the unpleasantness to be strangely strong at first — the mind does not enjoy losing a habit that reliably worked. It fades. Not to enjoyment, exactly. To something more like neutrality: a minute passing, and you in it, unbothered.
That is the whole skill. It sounds too small to matter. It is upstream of nearly everything.