A constraint I am working under now is an absence of an "h" key on my keyboard. A little nubbin under a keycap still works, so I can use an "h" regardless, albeit a bit more slowly and self-consciously. Imagine writing, every time you use a particular letter your finger got a tactile reminder of a letter you were using is special, and you're pretty close to my result.
If I were in an Oulipoean mood, I'd write exclusively omitting a letter from my text, and compose words only missing it. Absent a definite article, my efforts will refer only to one of many possible versions of a work, and never pin it down to a particular one. It's not so difficult, so long as you are willing to investigate synonyms as you run into words requiring a forbidden letter.
A style of Oulipo allows a writer to be self aware of a constraint, and to comment on it as one goes about doing work of writing. Formal restrictions on your work force you into creative patterns omitting or adding certain types of typical constructions. It also slows you down quite a bit, since a forbidden letter at a center of a keyboard is always a tempting target, and a large void to be avoided.
I'm glad for a task of needing to do some interesting avoidance of a key. It is a distraction from a temporary and transient annoyance, sure to be solved by a trip to a nearby Genius Bar, a place of keycap magic. I was careful to save all parts lost in my endeavor to do a self repair, alas at least one of my magic bits of plastic may be broken. I'm certain a fine Apple employee will be able to set it back to its original state.
Is it possible to keep your own voice as you try to write and always skip a missing key? Writing is like talking to a page, and if you are required to omit a fraction of your vocabulary as you do it, a great bit of easy spontaneity is lost. Surprisingly, a key in question albeit a frequently used one is not difficult to type around. A real obstacle is a need to be indefinite about objects referred to, but it is not impossible, just strange.
In general, a world we live in always admits a possibility of doing well by not always possessing precisely an item we are used to. If a car is not working, it's easier to take a bus, walk, or bicycle. If power goes out, we visit our friends from next door more easily. Dietary restrictions like a ban on milk products spur creation of delicious vegan treats. It's not always easy to make a transition away from routines, but new routines fall into place as backups to our usual well trodden ways.
I am writing in 750 words, a clever tool in its way of keeping track of not just words being typed but also sentiment and tone of a piece of prose. Seven score more words to write, and it's starting to feel like a burden just to get out words to make sense. So far a difficulty is a feeling of disjointedness, not so difficult to come to decisions on individual words, but connecting words are strangely missing and require odd constructions to work around. In a way, it's a struggle just to make sense at all. Of course it's also a bit late, and I'm tired, and it's a new year of its own.
My struggle is not a unique one in our family, as one additional keyboard is also missing keys. I believe a "c" and an "x" are missing from said keyboard, again posing compositional difficulties of late as I am led to believe. Working your way around a void is at first a struggle, until you obtain a pattern and meter allowing you to carry on regardless. I'll feel quite a bit better as soon as a new "h" key is put into place.