I came across this article from 2018 and it really spoke to me as a late-diagnosed autistic only just learning what “comfortable” feels like.
Too much text so my brain won’t let me read it and thus this might just be a summary of what you said, but
My take is to treat it like exercising muscles, you push as far into discomfort as you can handle (never reaching pain, pain is a sign of damage rather than growth), then you spend a long time resting and recuperating until you feel ready to push it again.