It's sort of a meme but I experience this pretty frequently with running. I've been a distance runner for over 30 years now but when I have a long run and I wake up and I'm just not feeling it, I will stare at my running shoes with pure hatred for a while before finding the courage to lace up and move. It's always the right decision, I always feel incredible once I get going, but it's sometimes very hard to summon the motivation at the onset.