you are marvelous
the gods wait to delight
This I would interperet as meaning you live your life to the full. You are a human being and have every right to enjoy life and when you 'pass over' you will be greeted with even more happiness and joy etc
you can't beat death but
you can beat death in life, sometimes.
and the more often you learn to do it,
the more light there will be.
those two parts
The 'can beat death in life' is refering to again, living life to the full. Don't be a couch potato or a nobody. A 'living dead' or Zombie-esque character lives a life of death. A nothing life. You will see more light the more you accomplish in life I guess and by doing these things, whatever it is that brings you personal reward, you are beating away the 'death life'.
The thing with poetry is it is how you interperet it as an individual. The author of the verse may hold a completely different interperetation as many other readers may. You should just read the words and enjoy. Feel what you want to feel from it.
Others on this forum may have a completely different idea of what the verse means to them and it will be interesting to see what their interperetations are.
Hope this helps