Non-Invulnerability

Oh to be immune to disease!
I would sell parts of my anatomy if I could just be immune to disease. Ok, I doubt I would actually part with pieces of me. But, maybe if I it comes in pairs, or has no real function I would go for it.
I have been laid low by another opportunistic infection. An invader has once again breached my once-potent defenses. I am become normal. Average. Yuk.
I feel that I must be overlooking some key to my health. I have been strong and resistant for several months. It is not yet winter, so why are my ramparts proving ineffective?
It is a quandary. And if I had a log of everything I ate and did for the last few months, perhaps I would see a pattern. But, I don't. Bummer. I will just have to stumble around and hope to hit on the solution.
At least I have a training log. So when it comes to training I can look back and see what works and what doesn't.
Now if only I was healthy enough to train!