I am a naturally optimistic, upbeat person. However, regardless of the stereotypes about people who see the glass as "half-full," I am aware that everything in Life is not peachy-keen. To me, being an optimist and avoiding negativity isn't about anything other that relishing the good times. It doesn't mean that I completely ignore the presence of negatives in my life or in others, it just means that I try my hardest to make the good count for more than the bad.
I don't think avoiding negativity means that you're putting blinders or rose-tinted glasses on...at least that's not what it means to me. For me, to avoid negativity is to not allow it undue influence upon my life or my choices. Notice please, that I said undue influence not just influence.
I am conscience, probably more than most, of the fact that the past, especially if it was traumatizing or terrifying, does have an effet on the present and, more often than not, the future. That being said, why give negativity any more power than it has already garnered through its presence within Life? It is because of this question that I choose to avoid negativity...and the reason why many others choose to do so as well. :)