Taking Things Personally

Today I am going to broach a subject which is really quite tricky, and as scientists I am not sure that we are really trained or prepared to do it.  My subject today is that we should not take things personally.  I know that we have all defended hypotheses in either public or private settings; but how many of us defend our idea due to its merits and not because it is our idea?  I am sure most of us say that it is always due to the merits, but is it?