Yes, all of the time! I think all teachers feel this sometimes to some extent, but I feel like it's worse in sped because no matter what I do, my kids are never "good enough."
Even if they're making growth, it's expected to be more growth than kids without disabilities, and at my school we don't have the resources to actually provide more intervention in sped (kids were already getting similar intervention in title 1).
Even if they're making more than one year's growth in one year's time, they're not passing state tests, so therefore still not good enough. My P wants to focus on the sped cohort for state testing next year because we're the only one not performing

.
Then if a child magically makes all of this growth with the very little services and supports we're able to provide, they no longer qualify for sped, and are therefore no longer considered a student with an IEP who is succeeding. There may be a momentary celebration when they're exited, but that's soon forgotten and the child no longer "counts" for me.
It sounds like your school is different, but in my school if a child were performing on or even close to grade level, he or she would absolutely be exited at their triennial review and there would be pressure to exit them sooner. In my state, students need to be performing at the 12th percentile or lower and show a non-response to interventions to continue being qualified as learning disabled.
I try to focus on the positives and the growth that kids are making, and also consider how I'm setting them up for "real life." I have several students who find every aspect of school to be extremely difficult; they need thousands upon thousands of repetitions to learn even the most basic concepts. Yet they have great attitudes and continue to work hard- a life skill that will serve them incredibly well when they're older, perhaps even better than the "book smart" kids.
My best friend is dyslexic and always reminds me that she is a perfectly successful adult without being able to read 200 wpm. I think we sometimes get so wrapped up in all of our stupid assessments and targets that we miss the forest for the trees, so to speak.