The nice thing about being autistic in a relationship with another autistic person is that there is a lot of mutual understanding and lack of judgement when you get overstimulated and as a result lose your ability to regulate your emotions and end up having a tantrum. On the flip side, being autistic in a relationship with another autistic person means that there is now double the chance that one of you would get overstimulated, lose his ability to regulate emotions and throw a tantrum. And in any social situation that you enter as a couple, there is a non-zero chance that both of you would end up overestimulated and unable to regulate emotions at the same time, at which point you end up in a negative feedback loop where you amplify reach other's distress instead of lessening it. And suddenly it's three hours later, you're both exhausted, things have been said that neither of you really meant, and you're finally calm enough to be like, "Wow, that was all completely unnecessary. We were on the same page all along" and start cooperating to fix whatever got broken.