Do you regularly feel sleepy in the day? Do you sleep well at night? Do you get sick very often or have any chronic health complaint?
Overcoming Illness during change of Season
You have likely noticed how when some "bug" is going around, some catch it and some just don't. Your own resistance to getting sick may have to do with how you answer the above questions. Relaxation...and sleep...are a repairative state. Getting sick is also a reparative state.
If we can listen and respond to our body on a regular basis, we may overcome circulating bugs. I sometimes notice a rare feeling of tiredness in the day, or sneezing. I believe those are early indications that my immune system is encountering an invader. When this happens, I pay closer attention. I also make effort to respond.
For example, today I am doing some computer work. At some point my body started feeling a little uncomfortable. So I took a pause from sitting at the screen to stretch and move. Sure enough, I felt perfectly fine in my body as I returned to my work of the day. Similarly, I just let out a little sneeze. I do not have allergies. I was exposed to someone who was rather sick yesterday. I am guessing my body is fortifying my health with that sneeze. I have a nice hot cup of water beside me at this moment. Glad I am feeling and responding to that impulse to stay hydrated.