if there's only one thing

I understand the adage goes: 'You can't have everything you want,' meaning you'll need to make important decisions in life of what to pursue and what to sacrifice.

But what if there's only one thing that you've decided that you want? Anything else - any possession, any dream, any memory - is secondary... is worth sacrificing if you could just have this one thing because maybe it is everything you want, and maybe you never knew it until now...

How does that work?

Can I have it?
I think I'd give up anything just for a shot... just for one chance to prove that she's worth it _ __ ___