I saw this on last week's parsha, which I thought was amazing (haven't had a chance to type it up until now).  It's from sefer Kol Eliyahu, selected chidushim from the Vilna Gaon (I will paraphrase.  It does lose something in the translation, but I think this is worth a shot):

"Re'eh Anochi nosayn lifneichem hayom bracha u'klalah"
[See I am placing before you today a blessing and a curse]

It says "I am placing" instead of "I have placed."
"I have placed," would mean that a person can only choose a good path at the beginning, but once he has chosen a bad path he is stuck with it.  Therefore, it says, "I am placing."  A person has the chance any time to choose a good path.

A person might think, nevertheless, what good will it do me to choose good?  I have accumulated so many aveiras in my life.  Therefore, it says "Today."  Whoever does Teshuva should view himself as a newborn baby.

A person might yet say, "what can I do if the yeitzer hara shall force me to sin."  Therefore the verse says, "I."  God, Himself, will help; you need not fear the yeitzer hara.

A person might say "this only helps if the whole world chooses the good path.  What if I'm the only one who chooses good?  What is it worth?

Therefore, the verse says "See (singular)."  Choose good for yourself regardless of what the rest of the world is doing.