If you exercise regularly, donít be afraid to take time out for vacations and illness. Make sure you have one day of rest each week. Sometimes having a break allows us insights into new ways of working, and builds up enthusiasm when we feel jaded. If you are training very hard, for a marathon perhaps, be aware that you run the risk of depleting your immune system. In one study people who ran the Los Angeles marathon were six times more susceptible to a cold or the flu than those who exercised regularly but didnít run the race.