Make time
If you are one of those writers who insist that you can only write when you sit behind your desk, wearing your slippers, with tea in the cup and the door closed, try to challenge yourself. Try writing a few lines the next time you have a wait. You can write on your mobile or on the back of the memorandum.
Just try to get a little down.
Describe the feeling you got when the health fanatic passed your carriage and gave you a look when she saw you had creamballs in the carriage. Or your annoyance about the long queue at the vending machine, which again was broken. Or write further on the phrase you heard over by the cold counter.
It can turn into a lot during one week. Especially if you usually only have time to write on weekends.