This is just an observation that I've made over the years: when coming off a cold or flu, go easy on the hard cardiovascular conditioning. Lifting weights is fine, but cardio(love that word) seems to crush your immune system and set one back. Also, start off light when you get back- walking first- then see how you feel the next day. Then you can crank it up a little. Have patience with it.
Had a fascinating conversation with John Schaeffer from Greyskull Barbell today. Now John is a cool dude and has some great training and nutrition insight. He is one knowledgeable mf. Anyway, he was saying that all the dieting and perfect training under perfect conditions is all well and good, but it ain't necssary. He was talking about prisoners. They are on a schedule, regimented with their meal times, their training times, their lifestyle. And most of them, in his estimation, are in great shape. They have shitty food, shitty weights(some just chins and dips) but they get in great physical shape. You know that they are eating lots of white bread and rice(carbs!!!, oh no!). Whats the secret? Being consistent. Just getting it done everyday. He said that he has an article 2/3 done about this and I can't wait to read it.