Everyone has a wall up when dating (and if not, you should!), but there’s a difference between being careful to not reveal too much too soon and having your heart guarded by the U.S. Army Reserves.
On a first date, whether you met on JDate or not, keep it to the basics: where you grew up, where you studied, and where you work. You can also cover a VERY brief recap of your relationship history (divorced, widowed, children), where you’ve traveled, what your hobbies include, and more general topics like such. Your wall should keep you from revealing more than that in order to safeguard your heart. If you get into your sob story or discuss other intimate topics — and then never hear from your date again — you’ll be crushed that you opened yourself up to someone who is basically a stranger. Wait until something develops first. In the meantime, find commonalities and build on them, revealing a bit at a time so that your date knows that you’re interested and interesting.