One of the things that you can try is the stop-start technique. Where your partner gets close to orgasm and either you or your partner firmly squeezes the head of the penis which will take away the urge to ejaculate. When this is done repeatedly a man can get in touch with the urge to ejaculate and become more in control of that urge. I'm healthy and I work out, but recently I had a problem maintaining an erection during sex. The first thing is to not worry about one episode of not being able to maintain an erection.
Sexual dysfunction happens to everybody at some point in our lifetime.
Sex therapists refer to sexual dysfunction as problems that are recurrent and persistent. So not getting an erection one night is not a problem. But if you think it is a problem, it can cause a fear of failure where your thoughts about not having an erection will lead to not having another erection. Some of the things that can cause no erections are alcohol, emotional things like anxiety, depression, guilt, anger and many of the recreational drugs. Now it's practically nonexistent.