Never forget about the power of smiling and keeping a positive attitude. Just because life has you down in this very moment, doesn't mean that you shouldn't be able to smile. We must note in our every day lives that we are the catalyst to reaching our destiny, and the things that we do to maintain a positive attitude like keeping a smile on our face during the worst of times help us to overcome adversity in the worst of times.
Also note that continuing to smile in the midst of adversity is what can help to bring others through their situations in life as well. Never take for granted that you may be the example that others are following in their own lives, and when they see you continue to smile when you are discouraged, they will do so when life seems to get most difficult for them as well.
You haven't lost your smile at all, its right under your nose. You just forgot it was there.