I’m 62 years old and have to be in the right state of mind not to attract any disease which would start to finish me off. All bacteria and viruses are opportunistic. There is no explanation for many diseases so far and the main culprit are usually viruses.

I don’t know why but a lot of people forget that antibiotics only kill bacteria.
Sometimes viruses are used to our benefit to fight off some other diseases. The host = the patient is infected on purpose (I think to fight off some type of cancer)

Anyway one has to remember that once one is unhappy then is/her immune system, gets weaker. Co if you want to live long (which I do) then you can’t to afford being unhappy.