A cold is generally just a sign that your body is worn out and telling you to take it easy, so it can repair itself. After colds is when the immune system is at its healthiest, but healthy eating, exercise and sleep can also decrease the chances of you getting a cold virus. If you have a cold, after blowing your nose, wash your hands and try not to touch your eyes, nose or mouth. If the weather is rapidly changing, it can also be a sign of hay fever. The best way to not get a cold is by simply looking after yourself, and to be very hygienic. Keep in mind that different seasons may contribute also to you getting sick, and colds can be very contagious. :)