The athletes who achieve their goals are the ones who are able to weather these lulls, and find motivation and confidence to get the training done when they doubt they can or aren't sure they want to. If they can't find it, they fake it. Seems odd, but it works.
Sometimes you have to fake it. Your body doesn't know fake attitude in hard training. It only knows hard training. Your goals don't know fake attitude/motivation/confidence. It only knows do, or do not.
You might not want to go to work, but you smile at your boss and co-workers, despite knowing you'd rather be anywhere else. (Maybe even on your bike, or training in the cold!)
I know the weather sucks around the country right now, from So Cal to the Northeast, and your motivation lacks. Fake it. Get on that trainer, get out the door.