Best for a cold is forgetting about work, and rest. I realize this might be impossible but it is something should be given serious consideration. Think: if you notice the signs of a cold, if you take a few days off, rest, drink a lot of fluids, take huge quantities of vitamin C (preferably from fruit or vegetable juice), you probably get better in a few days, maximum a week, if it's a really tough virus or you are weak (due to stress, to much work and so on).
If you neglect it, going to work, it will heal in much more time, and you might need antibiotics. (not against the virus,because they are not affected by them, but for the bacterial suprainfection what usually occurs)
It is hard to just relax and not do anything, but it is exactly what you need to do. Also, as far as I know, it is advised not to do any yoga when you suffer from an acute illness. The body has it's own intelligence, much wiser than our average conscience. Let it do it's job. beleive me, it does everything it can to get you out of trouble. Trust it, and all will be allright.
Anxiety usually makes the immune system weak. Any kind of anxiety. If you are anxious to continue your practice, you weaken your immunity. Any kind of agitation, restelessness of the mind just works against you.