Help I need an advice on having my machine to work properly

First of all, I ́m not that experienced having sex but I know I ́m good on previous teasing and pre-sex in general. The thing is I applied some text game and had a girl comming over to my place. We talked, drank some beer, and pushed the interaction forward. Everything was going perfect until sex, I couldn ́t keep my erection strong. First time occuring to me, I ́m kind of dissapointed to myself. We tried more than once but I just couldn ́t keep it. Has it happened to any of you? I haven ́t slept well but not sure that ́s the problem. anyone can help with this?