Before I eat anything I was my hands throughly for about 30-60 sec.
I hold my breath when walking past other people.

But I still catch the cold. Why?

there is no complete way to prevent yourself from catching a cold unless you live in a bubble. You do the best you can to prevent it, but it only takes one small spec of germ to get into your system. It can also depend on your immune system. Some people are more resistant than others.