How can the Bhagvad Gita help guide our lives?
Before we can answer this question, let us look at what happens in the Mahabharata. Essentially, for some reason or other, God or some other such abstraction has decided to kill off lots of warriors. A few are fated, for some reason or other, not to be killed. They are called the 'victors'. Everybody else dies.
At the start of the Gita, Arjuna is depressed because he foresees being one of the survivors. He decides not to fight. Krishna explains to him that refusal to fight would be to go against his own nature- he is a warrior- and won't change anything anyway. Eventually, Krishna shows Arjuna that he himself is actually God almighty so, like, everything's cool, don't sweat it bro.
The Gita is a very important guide to Life because of the large number of shit-heads we have swarming around who claim to be God Almighty or possessed of some higher Moral authority or Magical power and they want us to go kill lots of people, or hand over lots of money, or give them a blow-job or something. JUST SAY NO. They will then tell you that they don't really need your help, it's all going to happen for them anyway, except you don't get to go to Heaven. PISS ON THEIR FACE.. Unless there's an actual job with a good pension and dental plan in which case don't piss on their face but remember ALL BOSSES ARE ASSHOLES. Take the job if you have to and dunno, like maybe do Yoga or something when you ought to be stock-taking and remember to steal as much office stationery as you can lay your hands on.
So that's the Gita as a guide to life. Tomorrow we do the Bible on how crucifying unmarried Jewish carpenters is the best thing you can do for Humanity.
(Why am I wrong? Can philology, can hermeneutics, give better answers to this question?)