Ok...Ill give yah a serious answer.
There is only limits you set apon yourself...no human, be him child or adult, has a limit on his/her heart.
If you want something, and are tired, but still believe, then you can still fight.
It depends on how you feel about it, and remember, breaks are allowed.
Like me...I dont give up on things for a while...until such things get close to getting me fired or kicked out of something, but even then I like to try and knock it as close to the edge.
If yah wanna fight, fight...a Heart never gives up, until you want to, you are your own man, no one controls you.
(Joke answer: When the guy with the gun aint smiling anymore)