Make your heel sandals come out as you masturbate. You’ll get a “afraid your sandals come out” tinge of sexual fear of losing your sandals, that your sperms shoot out in heightened pleasures. I know it because I do the same on stairs.
Your cock will feel a deep sucking retention as it pulsates as you experience the resistive coming out heel sandals as the lost of your toes gripping your sandals overwhelms the ejaculation intensity.