I think most guys tend to obsess too much when they have had an issue. Then the next time they have anxiety (“oh I can’t let this happen again!”), and consequently, have more performance anxiety and less fun every time they do it.
If it’s a new girlfriend, it is perfectly natural to be over-excited and come quickly, it may not be the perfect experience for her, but just communicate. It happened to me in my late 20s with a girlfriend that made me wait forever and was super-sexy. I thought of myself as a stud at that time, tons of experience and great feedback from many women, and then with her I come within 20 strokes, unable to control it. And you know what - she was incredibly flattered. :-) Especially since after I adjusted to her (tightest girlfriend ever), we could go for hours. Damn I should have married her, but those were my playing days and regretfully I ended up f*cking it up (she made one or two bone-headed decisions herself). And the first time I got together with my current GF, I also came quite quickly. She laughed, said “wow that’s a lot of cum, guess he likes me” pointing at my penis, and I laughed, and then she said, “you know we will have to go again, honey, right?”, and after letting me rest, she sure made sure to get hers. I think that’s the way to handle occasional “mishaps”, with humor, and not allowing performance anxiety to trickle into the next time.
To me, the key is to enjoy every time. If you harbor doubts and anxiety in your mind, deal with it, and *don’t* do it because it means you’re not ready and you’re not really in the mood. You’re only ready when your head is fully committed to enjoying the experience of utter joy and ecstasy with a person willing to share such a moment with you, and treasure every second of it. Without storm clouds in the back of your mind.
Unless there’s a health issue behind it, it’s in the head, and the key is to work on simply dismissing such situations as comical stuff that happens to all of us, and will happen again. I’d be totally lying if I said that my dick has been up to the job every time, but then it ain’t my dick’s fault - it’s my head’s, and it’s time to maybe think or relax for a bit longer, and then it always works out. We’re not fuck robots. Just figure out what triggers you, no one else can tell you what to do about it, this is the kind of thing that probably sits somewhere deep inside, and only you can honestly assess it. Just relax and realize there’s nothing wrong with you, you function perfectly (it could be much worse, believe it).
PS: I’ve never had a *bad* ejaculation. They always feel very good and I don’t regret a single one of ‘em. :-D