How can i avoid getting sick in the future and especially during cold and flu season?

Many: Rest, fluids, avoid exposures to extreme heat or cold, perhaps some low dose vitamin c. The best of all is washing your hands, and wiping down surfaces and keeping your hands away from your face. If you are rested, hydrated, eating nutritiously, sleeping 8 hours, and using good hygiene, that is about all you can do. Hand sanitizers help. Avoid being around those you know are ill.

Sick: Good question but no good answer. Drink lots of fluid, eat a good diet, get rest, avoid steam rooms in the gym, avoid frequent flying and contact with young children