What doesn't kill you makes you stronger

a couples of days ago i got this song from one of my brother
i've heard this song before....
but i don't really know the meaning or try to find out the meaning of the lyrics
and i don't know why when i listen this song, not from the truly singer (Kelly Clarkson) but i heard from one person who recover this song, accoustic version....
and i really interested with this song

my favorite lyric
You think you got the best of me
Think you've had the last laugh
Bet you think that everything good is gone
Think you left me broken down
Think that I'd come running back
Baby you don't know me, cause you're dead wrong

What doesn't kill you makes you stronger
Stand a little taller
Doesn't mean I'm lonely when I'm alone
 
What doesn't kill you makes a fighter
Footsteps even lighter
Doesn't mean I'm over cause you're gone

What doesn't kill you makes you stronger, stronger
Just me, myself and I
Thanks to you I got a new thing started
Thanks to you I'm not the broken-hearted
Thanks to you I'm finally thinking about me
You know in the end the day you left was just my beginning

and you know what guys??
this song had been a nominator for many category on Grammy Award 2013
such as Record of The Year, Song of the Year, Best Pop Solo Performance, Best Pop Vocal Album
and Kelly Clarkson won for  Best Pop Vocal Album - Grammy Award 2013
sounds awesome didn't she??
wooohoooooo :)