There is no clear reason, but for many months already, I have almost given up running – Which is a shame, as I enjoy it so much. And yes, I can talk a lot about why not, but –outside of one seemingly stupid point– there is really no reason.
And yes, I have taken on cycling, although on a very different fashion: Cycling is by far not as good as an exercise as running – Yes, cycling for ~1h on average 3 times a week has kept my body from becoming sedentary again, but I do feel some increased clumsiness and a undeniable weight gain that I don't want to allow.