how do you know when you have way to much on your plate?

i really need help.
I really want to write another story and i just dont want to start it but not finish it.

I'm really fast writing chapters and i make sure that i dont not finish it.

So i need opinions on when do you know that your have to much on your plate?
I really want to write a new story but i just need opinions and stufff.
And if someone could check out my story to tell me it's god or not, just kinda like a review.

Thank you very very much. =]

http://stories.mibba.com/read/326345/One-Little-Thing/