I masturbate daily ( once a day once in a while twice ). Last month, my girlfriend and I were about to have sex, and I just couldn't stay/get up. This month, I changed my mindset, I was too worried about my erection and I was not focusing enough on my girl. So I just focused on my girl, cuddled kissed touch feel everything and walllaaaaaa I got a hard erection, and it felt really hard. Maybe some of the other people who are having trouble just focus too much on keeping up which results in a psych out.