I get similar from time to time. It's not as alarming as it sounds, but for some reason I just suddenly will lose all motivation, lose all will to improve, a kind of feeling that you just want to "exist" rather than do anything important (which is such a polar opposite from how i normally treat life).

I think it's some manifestation of burn out for me, but if I take the cue and take it easy for a few weeks, the creativity and will to improve always comes back.