Not how good they are. Just how stable. If you say they don't change, that's because they don't change; doesn't matter if you can always do calculus or never know what a number is. I'm not asking for how good you are, but for how much it varies.
Mine are pretty stable. My executive function predictably starts out half-decent and over the course of a day invariably is almost totally lost except during my "second wind." Other than that I mostly just learn things and they stay learned. Sometimes I forget unused knowledge. So my abilities today are probably pretty close to my abilities tomorrow. Tomorrow I may be slightly better, but probably not over such a short period of time.
On the other hand, for some people, abilities today say nothing about abilities tomorrow. And for some people, they learn and are solid on what they learn, but they learn really fast and really rarely. Some people report shutdowns.
Stress, of course, negatively impacts most people's abilities. But here it's kind of a question of degree. I'd still say your abilities are linear if, faced with great trauma, your social skills fly out the window while you're melting down over something really, really awful. But if your abilities are unusually vulnerable to stress...
So just answer what fits you best. (If you have regressions and lose abilities, but these are abilities that are NORMALLY lost, like the ability to soak up a new language in just a couple of years just from hearing people using it, then consider yourself to not lose abilities. Even though that makes no sense at all.)
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I'm using a non-verbal right now. I wish you could see it. --dyingofpoetry
NOT A DOCTOR