Cock rings?

I recently brought a few different sized rubber cock rings to try. I'm not getting as hard as I used to and was hoping they might help.
I've tried a few different ways of wearing one. Just around my cock and around my cock and balls. I don't find they do particularly much and I'm wondering if I'm missing something. I have to have one on just my cock and it has to be very tight. My cock will get swollen but not overly hard.
Just wondering what peoples experiences are in this regard. I have a session booked in for tomorrow and I'm hoping I can make some adjustments to impress the wife again.
Thanks.