I've had the same thing happen to me multiple times before, often a couple of weeks after kinda letting go of RCing and WBTB. Most of the time it motivated me to continue at it which might be your mind's strange way of telling you not to give up

But I do think it could be to do with stress, because for me personally, if I think about something too much, I often find it hard to comprehend after a while/think clearly about it, kinda like when you say a word 20 times and it loses its meaning. That means sometimes I'll have trouble completing reality checks and even if I try hard not to, I might end up going into autopilot mode while doing it. That's also an issue when trying to do stuff like self-awareness.

Maybe taking a break lets your mind process the work you've just done in terms of lucid dream practising and lets it put the stuff you've learnt to use? Like how when you revise something, you get better results when coming back to the topic briefly again a little bit later, and how when doing a sport/physical activity, too much all at once will damage your muscles rather than improve them?