When motivation is lacking, the only approach I know is to keep on moving, to go through the go through, to do the next right thing, and then the next, the best I can, even if my brain is murky, even if my muscles ache. And inevitably, the spirit engages, and energy rises within, and I warm into the day in stages, until I feel fully alive and happy yet again.
If the day comes at me hard, I just go through the motions, and trust the momentum of my movement to carry the spirit, until the spirit can take over and carry the day.