Yours, theirs and its don’t take an apostrophe when they’re describing something that belongs to someone. Just like hers and his don’t. So, it’s George’s book; the book is his. It’s your book; the book is yours. It’s their book; the book is theirs. It’s the book belonging to the club; it’s its book. No apostrophes. The only apostrophe that comes along with yours, theirs, his, hers or its, is when it’s stands for “it is”.
So it’s never your’s – it’s always yours. If it belongs to you, it’s yours. Not your’s. Not their’s. Not it’s.
You’re means “you are”, like they’re means “they are” – your means “belonging to you”.
If the widget belongs to you, it’s your widget. No apostrophe.
“You’re improving your health, running regularly. Is that your sweatband? Are those trainers yours?”
Short but sweet. Now you won’t forget, will you?
More on apostrophes here.