Internet is full to the brim with different answers concerning your question. Here is one of them:
When things turn sour, try to make them sweet.
Turn something inedible into something to eat.
When you hit bottom, look to the sky.
At the edge of the cliff? Spread your wings and fly
Everyone falls. So get back up and stand
Learn from mistakes, keep giving a hand
Life isn't about perfection, it's about doing the best you can
It is through experiences both bitter and sweet that you gain wisdom you need to be a man.
Recently I read another opinion regarding this phrase:
"Americans are fond of saying "If life gives you a lemon, make lemonade". With Bush in the White House the United States has become the world's leading producer of lemonade."
Student or Learner