Weird sense of calm

For the first time in a really long time I have started my weekend feeling pretty calm. I find it difficult to relax and am a very anxious over thinking. Calm is not something that comes easily to me so it's not a particularly familiar feeling. Randomly this weekend I feel much more relaxed than I usually do (not totally relaxed but an improvement for me). I have no idea what has caused this calm feeling and I guess I should just appreciate while it lasts. But is it weird that I feel slightly thrown by this feeling. I'm so unused to it, my brain is a bit on the defence like why are you calm, you're not supposed to be calm you're supposed to be vigilant.