Try a dozen or so rides at one PSI. Then ride another dozen or so rides at another PSI. Then ride another dozen rides at some other PSI. Which felt better to you and left your legs feeling like they had more energy to ride more? Which does your data say that you did better times on?
That's your personalized optimum PSI for that road surface and tire. If you happen to get pinch flats, then your PSI is way too low for that riding surface regardless of how good it felt.