Every year you're likely to get a cold, perhaps several. There are simple ways however to reduce your risk of catching an infection, reduce it's severity or improve your ability to recover.
Wash your hands
It's simple, and we should all be in the habit of doing it as responsible medical practitioners. Within the hospital take care to follow the 5 moments of hand hygiene. That patient's room may seem innocuous but you probably didn't know they were up all night with gastro. Keep in mind though, whilst the patients may be the sick ones according to the files, many hospital staff members will also be sick. It is within our hospital's culture (rightly or wrongly) to push through that cold or flu in order to keep providing health care. So it's your responsibility to protect yourself, protect your patients, and protect your family and friends back home. Speaking of home, a simple measure like washing your hands twice with soap goes a long way to reducing the bacterial count on your hand. The CDC recommends singing Happy Birthday through twice to ensure you've washed them for long enough.
Sneeze into your sleeve
If you're going to sneeze, do so into your sleeve or shoulder. This will spare your hands the onslaught of germs and prevent you from accidentally spreading them if you touch objects and people, or even reinfecting yourself should you rub your eyes (or pick your nose!).
Get some rest
Those long hours aren't going to help your body. Get some rest, even if it doesn't physiologically aid in fighting the sickness, getting more sleep will reduce the feeling of tiredness that comes with a busy schedule.
Choose fruit and Veg over supplements
There has been various degrees of evidence (or lack of) saying that supplements aid your immune system in times of sickness. If you believe they are helpful to you, then it won't harm you. Consider changing up your vitamin supplement to fruit and veges though. You get the same contents along with all the other benefits of fruit and vegetables.
Throw away used tissues
It's your mess, not someone else's. Besides being disgusting, bacteria and viruses can survive on those tissues for a short window of time and it's just not polite to spread those things around.