I was also thinking the other day that I haven't caught anything for quite a while. There was a terrible bug at my school in February (similar to Covid but no one was ill enough for it to have actually been Covid). Because I had been watching and reading the news about C19, I deliberately distanced myself from everyone, took Chinese friends advice about airing rooms, made students sit at the back of the classrooms, washed hands etc, and managed to be part of the 10% of staff NOT to catch it.
I wear a mask all the time I am out now, even at work while I am teaching. I wash my hands repeatedly and am only around others when I have to be.
Miraculously, the the result of this has been no colds or bugs. I usually catch everything going, so it has to be because of my careful measures.