>>12710950like a muscle, the reflex needs training.
Practice by saying what you are going to do, then do it.
Start small. Make tea or coffee if you are totally incapable of other goals. Otherwise say something big.
Learn what your time threshold is.
If you say.. "I'm gonna do 20 pushups now" how much more/less likely are you to do it when compared with saying "I'm gonna do 20 pushups in 30 mins" or even "tomorrow".