If you are positive (unwittingly or otherwise) every contact you avoid reduces the R number.
Yes, you may still pass it on at work or school but if you don't have drinks with the neighbours or have kids over for tea, you won't pass it on to them and therefore the R number reduces.
Not perfect but it will help...unless everyone keeps saying it's all pointless and no one complies.
If that's what you're doing, you are the problem. Last time, people largely complied because they wanted to be seen to do the right thing. Now we seem to have created a situation where it's perceived to be a bit wet to follow the rules.