Actress Vishka Asayesh in the Swiss marathon

It is a very rare marathon runner indeed who gets to the end of the entire training block without missing some runs, whether it's down to illness, injury or just life getting in the way. A few days off, or even a week, will make very little difference to your race day. The rest might even do you good. If you've missed a bit longer – two or three weeks – you should still have time to build up to your longest runs, which are really key to race-day success.